I might consider getting into W7 again soon, and I don't like changing classes (at least not in Wizardry's implementation). And I have my own vision of dream party (Lord, Valkyrie, etc.). However, attempting to create new character allowed me to choose only from basic classes, and only after that choice game allowed me to distribute stat points.

Is stat roll made "behind the scenes" when you choose class or game strictly limits you to Base Classes?

And if you can make Advanced Class from the start, how hard is it to roll them? I think I speak in terms of 21 stat points roll (my party is going to be human-only).

The roll is made each time you go through character creation. If you want to create an advanced class, you need to get lucky. Also, it helps to choose a race with good base stats in the stats required for the advanced class.

Is there any particular reason you are limiting yourself in terms of racial selection?

Incidentally, Wizardry 8 got rid of the randomness in character creation and allows you to choose any combination at character creation. Of course, some combinations are better than others (in my current playthrough that I just started, my Dwarf Gadgeteer started with -10 bonus points, as opposed to 50 that my Dwarf Priest started with.)

In case you are wondering, my Wizardry 8 party has no humans, but my Bishop is going to be human. I am not ready to create her yet (I'm about to brave Arnika Road for the first time on this playthrough.)

So how feasible it is to roll for Advanced Classes? E.g., in Elminage games I never saw Ninja on start - that's after rolling a dozen or so of Lords. From what I see, Lord is the most difficult-to-roll class in W7, so how difficult it is to roll Lord in comparison to Elminage's Ninja? I like to have humans' only party because it feels more right (especially after playing Wizards & Warriros with elephant people in party) and also because humans are usually the most well-round races without specific bonuses/penalties. I make exception for MM games, because MM default parties are considered canon (well, up until part 7, when characters went through race/class changes..., still I consider them canon just named alike MM 6 heroes) and are well balanced. Yeah but I avoid Wizardry 8 because of level scaling and some other moments. I don't even consider it as true Wizardry for many reasons.

I'm not sure about Wizardry 6 and 7, but in Wizardry 1 through 5, humans are actually not that good; they have a weakness (low Piety), but no advantage to compensate.

In versions of early Wizardry that cap stats at base+10 instead of 18, I find that the best races are Dwarves (high Strength and Vitality) and Hobbits (high Agility makes a huge difference).

But Dwarves had lower I.Q., Agility and Luck. That's why I say humans are the most well-rounded race.

Also Wizardry 6 and 7 have different game systems from W1-5. From what I know so far, all main stats are capped at 18 via leveling and at 20 via using ankhs.

Reading other sites, seems that getting 21 bonus roll on creation is quite possible, but people don't say how long it took them. E.g., people say that it is possible to roll Lord on start in Wizardry V, so I got stuck on character creation screen for what was like couple hours with no luck.

I had a glimpse of W6/7 before but was distracted bby other games. There was patch by MadGod to make fast resting if you don't mind altering officially intended mechanics. This patch is integrated in new version of Cosmic Forge along with various bugfixes.

Level up mechanics are actually quite cool - you get base magic resistance increases and things like this, instead of raw HP. What concerns class changing, well, I am not fan of it in general. But you underestimate how broken class changing is in W7. You can learn top end spells while being Level 2 and having a total experience of around 20k - all this through extensive class changing.

I am also not happy with timers, but from what I know, you can't make game unwinnable if you take too long. You can always find those NPCs and beat all the quest items out of them. Those timers are a small evil in comparison to WTH Arnika Road massacre and other horrors of level scaling in W8.

Just launched newer Cosmic Forge in preparation to apply bugfixes and found description of roll mechanics.

~ Chances to get Attribute bonus points:
1d4+7 (8-11) points is 66.667 in 100 (800 in 1200)
1d6+4 (5-10) points is 31.583 in 100 (379 in 1200)
1d6+12 (13-18) points is 1.667 in 100 (20 in 1200)
1d6+20 (21-26) points is 0.083 in 100 (1 in 1200)

So if I am not mistaken, Human Lord requires 21 pts, so the chances are...

Edit: I think I will use Cosmic Forge's Stat Roll patch and will modify classes and level-ups to give constant HP and Hit Chance increases, instead of random, and will make Special/Death Resists increase with level ups. But situation with Mana Regen looks ugly, as it is static value.

Humans can choose all classes with a roll of 18. Lord needs 18, Ninja 17, the other classes 3-15 (Female versions might need 2 more) so it should be doable within a few hours if you roll quickly.

Yeah, when I said 21 I looked into Faerie Lord requirements by mistake.

My party is ready already :)

One other thing: Valkyries are easier to qualify for than Lords and I believe they level up faster. Lords have no significant advantage over Valkyries in this game.

The readme is wrong. It's rather something like

~ Chances to get Attribute bonus points:
1d4+7 (8-11) points is 361 in 400
1d6+12 (13-18) points is 38 in 400
1d6+20 (21-26) points is 1 in 400

I doubt so, this info came straight from the gamedata with Cosmic Forge allowing you to choose alternative rolling system (weighted more toward higher rolls).

Cosmic Forge also shows all the hidden stats (Resists, Base Miss Chance, Initiative, Mana Regen, # of Attacks and Swings). However, I don't see direct effects of raising skills, I can only guess how they work.

In Wizardry 7 it's impossible to roll lower than 8 so there's obviously no 379 in 1200 chance to get a 5-10 roll as end result so there obviously must be a mistake.
You also get 13-18 far more often than every 60 rolls, i guess the readme was messed up and should be (fits to what you usually get when rolling):

1. roll for 5-10
2. 1/20 chance for +8
3. 1/20 Chance for +8
4. if lower than 9 roll for 8-11 instead

Over years and years of rolling characters in Wizardry 7, I discovered that for each new game session, the SECOND character you create will always have a highish stat roll. (At least it did on my game, every time, but my version is a CD-ROM build with a later copyright date than what GOG has.) I would usually make two characters, quit the game, and restart, and it saved me a LOT of time when I was trying to make an elite class. Nowadays I've just applied the algorithm patch from Cosmic Forge and it saves even more time.