While info on JA1 outside those stuffs is pretty close to non-existence, there is at least couple of easy to find counter-to-some-extent-examples: some old and good for its times, but pretty obsolete by now guide of mid-90s; and page by Blueskirt, containing data from the book Jagged Alliance Strategy Guide by the great Brenda Garno.
https://www.gog.com/forum/jagged_alliance_series/jagged_alliance_1_strategy_guide/post85 As this page contains a really useful and structured data its of a really good value. Sadly, it also contains some misleading info aswell, partially because of wrong data in book itself, but also sometimes due to wrong interpretation by page author. So i decided to provide an edited and more full explanations to the table values there, upgrading it to a better usability. As i dont want those edits to appear on Jawiki, ill post them here, providing the link to main page in Blueskirt's quote. Those edits are based on page's revision of June 3 2019 (even in case it will be edited later, its possible to refer to certain given revision in case in change history).
As this stuff will be mostly about game formulae used to calculate the values from the tables, ill add a mention of another obscure (and worthy some stuff on its own) mechanic possible affecting them - Breath. Most often it modify the calculated value as a simple percentage [FinalValue = Value*Breath/100], but there could be also other factors to affect it beside. Other difficulty with Breath is inability to check its actual value by in-game methods. But as knowing if Breath affect a given calculation or not is useful even in "compact description" i'll mention it in comment to a values being explained below (ofc course Breath could affect only field-based mechanics).
All the values in tables are listed for a given merc with not changed starting stats and full breath. Note that i didnt checked all the actual numbers in tables, and, while i will mention some wrong ones i did notice, it doesnt means that not-mentioned ones assumed as having a right values.
Note, that all calculations below are in whole numbers.
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"APs: Shows how many action points a fully healed and fully rested mercenary can regenerate in one turn. Also remember that up to five unspent action points can carry over from a previous turn." Good one to start with:
[CurrentMaxAP = (MaxHealth + 2*Agility + Dexterity + 10*ExpLevel + 10)/20] Affected by Breath.
Min AP is 8, max is 25.
Note, that due to game bug AP value is also penalized by BandagedHealth, instead of being benefited from it. Command line option HEALTHY of patch 1.15 provide an optional fix for it. For more info about Command line options see patch 1.15 Readme.
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"Traits: Shows tendencies a mercenary has:" Merc could have only one trait.
No trait: no trait-related effects.
"Extremely Nervous: Will whine if not accompanied at all time." This one is very simple and correct: once per every game hour, merc with this trait will complain in a message if not having an other merc in 5 tiles radius. No other game effect.
"Forgetful: Will forget orders at the cost of APs." Have a 1/15 chance to stop per tile, but only if amount of tiles already passed for a given route command is more than 5 in turn-based or than 15 in real-time (so there is 0 chance to stop for tiles 1-5; 1/15 chance for tile 6; 1/15 chance for tile 7 and so on). In case of triggered stop in turn-based, merc will also lose AP's equal to roll from remaining AP's at the moment of stop (for example 100% 1 AP in case of 1 AP; 50% for 1 AP and 50% for 2 AP in case of 2 AP and so on). Exploitable, as player can easily prevent a trigger by ordering move not further than 5 tiles at time. Require attention in real-time tho, as stopping in a bridge would likely causing mercs who follow Forgetful one to try to went water instead, as a new possible route.
"Hopeless Shot: Marksmanship improvement is a great challenge." Very simple one too: the calculated chance for an experience roll for Marksmanship is divided by 5. No other game effect.
"Snitch: Will report on any dissatisfaction your team might have with your management. Although unrelated, in Jagged Alliance, mercenaries with this trait are extremely loyal and won't steal money found on the battlefield. This is not always the case in Deadly Games." Will simulate for every other merc a check for Fatality (called as Death in table), Turnover, Non-Payment, and Fail rates as if its already a next day, and rates values increased on 1 each. In case merc will reach the amount to complain, Snitch will report it with message. While Snitch in charge at current day will not report about self, having more than one Snitch in team would lead to choosing one of them in random over course of days to work.
Dont know about Deadly Games, or from what idea about "although unrelated" appeared, but in JA1 Snitch trait directly affect if the merc in question will steal money or not. While Snitches also technically have a need to get a hand on a cash 99 times their salary to steal, and while its not really possible in non-modded game, even if you will modify the steal value or salary of a given Snitch merc - that merc still will not steal any money. Because being Snitch (or Native) is directly related to it - to not steal money they carry no matter the sum.
"Heat Resistant: Unaffected by the heat waves that randomly rolls on Metavira. Native Guide: Native Guides are free of charge, give tidbits of info on the various sectors of Metavira, are unaffected by heat waves, receive bonus to avoid and kill Metaviran water snakes, are familiar with the Metaviran natives' language and are extremely loyal. Death or discharge of Native Guides do not affect A.I.M. death and turnover rates." Now its the complicated case. Those two traits mentioned above is an one trait in reality + some special treatment of certain mercs (Native Guides). I dont know why Blueskirt separated them this way, as the Book call them both "Heat Resistant". As i have to use other name for this trait ill try "Native" (probably "South-Atlantic Native" would suit more, as both Venezuela and Metavira fit it). To clarify effects of it, separation of actual "Native" trait and "Native Guide" is required:
Native trait (Elio, Hamous, Juan, Wahan, Hector + Guards + Tappers):
Not unaffected, but suffer 5 times less penalty from HeatWave (extra hot day).
Will not steal money (see Snitch above).
Native Guide (Elio, Hamous, Juan, Wahan):
Will provide info about sectors they currently are (note: not all sectors have messages, attributed to them).
Will translate a message on Metavirean from the Note in their inventory.
Additionally, all non-AIM personnel (NativeGuides, Guards, Enemies):
Will have a 5 times lower chance to be attacked by a WaterSnake when moving.
Will always re-equip a knife if attacked, and will get +40% bonus to roll VS snake.
"Non-Swimmer: Don't know how to swim and will rapidly lose their breath while swimming." Indeed, will spend 5 time more Breath while swimming. Also will suffer double damage while drowning.
"Over Enthusiastic: Will refuse to move or change target once they're engaged with an enemy. Have the tendency to kill teammates they dislike at night." The most complicated trait. Maniac (to shorten it) effects include:
Will refuse to move or change target if target is merc (no matter enemy or not), and that target is on the same tile still, that it was on when was chosen as target (so if target will move from initial tile it will cease Maniac effect), and if Maniac have a read-to-use weapon in main hand (so empty or jammed/broken gun will cease Maniac effect). Could be exploited to cease by removing a weapon from active hand or, as a way milder exploit, via swap-by-X (will not cease effect, but still move Maniac to other tile).
Will not forget own target when suffer a hit - so will keep a bonus of "firing the previous target". Non-Maniac mercs would still keep their weapons readied in this case, but would "lose concentration" on their target.
Will not complain if got friendly merc as a target.
Will generate more noise when moving (originally only when trying to Sneak, then changed to all cases by Sir-tech official patches somewhere prior v 1.13).
Will join player's team even if merc, hated by Maniac, is there, and will comment it with a threat.
Will kill the hated merc at the morning.
Will not care about other mercs being fired or dumped to a river.
"Wimpy Conscience: This merc will quit the team and resign from A.I.M. as soon he kills someone on the battlefield." Strictly speaking not "as soon he kills someone", but "the evening of day he kills someone". Despite invoking a Bribe process, actually cannot be bribed to stay. Still affect Turnover rate.
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"IMP: "Yes" indicates this mercenary can improve his or her attributes and skills either on the battlefield or through training. "No" means this merc cannot improve his or her abilities in any ways, and "Reverse" indicates this merc is a hopeless case whose abilities can only go downhill." Looks very good by me.