I'm thinking of making a Tiefling lawful evil anti hero type character with some Lovecraftian influences and flavour.

Can someone please tell me what the pros and cons are for these Magus kits.

Any advice on what to pic and what direction to take it in or what bloodlines fit would be greatly appreciated. Also I'm not massively familiar with the technical terms and abbreviations yet so if you can please make it as new player friendly. (idiot :P) as possible.

There is an excellent build guide on this site already, and you can probably find what you are looking for in there.

That said, of those three Scion is probably your safest bet, and if you take 4 levels of Dragon disciple (requires draconic lineage) it is also the most powerful.
Swordsaint really only shines at lv 20 at which point the game is basically over, and Archer is more of a multiclassing class.
Scimitar is the weapon of choice for magus, atleast in the base game.

This other dude says that sword saint is worse than eldritch scion. I couldnt disagree more. Sword saint is so unplayably overpowered its not even funny. You get AC bonus from your INT, which already makes sword saint better. Other than that, doing a pure dex dueling sword build with dips in aldori defender to get weapon training, monk to get extra AC and duelist to get AC, initiative, and extra damage, will basically make you immortal. With blur/displacement and mirror image, nobody will ever so much as touch you again, and you will be doing 4-5 attacks relatively early with 20-40 damage each hit, you will be pushing 50 ac without even trying. In other words: you will be able to solo the game easy as piss. Again, the dude mentioning eldricch scion might have had fun with it, but its NOTHING compared to sword saint...in my very humble opinion.

You may have noticed he wanted a new player friendly build, as in pure class and not a multidipping, ac stacking, min/max build, in which case i figured scion is considerably better.

My first playthough has just made it to the trading post after the tutorial. I normally start a few different games before i find something i like. I've also had a kineticist dark elementalist recomended for the lore side of things which seems interesting.

There is no reason to start a new class from scratch because once you get your city you have access to an npc which lets you rebuild your entire character, name and all (the first 3 respecs are free).

Kineticist is a very good choice when you are new to the various systems, and a fun class aswell.
It has simple mechanics and requires very little micromanagement. It also becomes the most powerful class in the game by a mile, although it starts out relatively weak.
The only downside it can become so powerful that it removes all challenge from the game, but that requires abit of planning.
For example, an earth/fire kineticist gets a late game spell that can kill just about any group of enemies in the game with a single cast, and if you add a level of monk to that you also become virtually untouchable with the right equipment.
Kindof takes the fun out of the game imho, but of course there are many less overpowered ways to build a fun kineticist.

Actually, said NPC is available as soon as you defend Oleg's training post.

Yes but she does not give the respec option then, or atleast she did not do so the last time i played.
That was a few emergency patches ago tho, so i suppose it could have been a bug.

Or you have disabled respec in difficulty options.
I also do not understand why everyone thinks Eldritch Archer is multiclass. I am playing it now, and she is like one volley just almost anything and from safe distance. Comparing to sword saint and almost all other story companion classes, she is way OP from the start, cause she has 2 attacks from level one, and keeps increasing rather fast on early levels. And that even before she gets Tenser, which turn her into literal arrow machinegun, with top attack bonus. Though, without tenser on, she can still jump around battlefield at will with dimension door and empovered maximized (yep, they stack) true strike ray in addition to 7 empowered attacks with sneak attack bonus 5d6 on top of bonuses from killer weapon and hurricane bow(sneak attack spell and hurricane bow spell after level 19) each can literally obliterate most (if not any) living thing possible just in one round.Oh, and forgot to mention, she can totally ignore enemy armor after level 15, and ignore agility with spending magus charges as well, (even though it's hardly needed with greater invisibility most the time).

I already found the respec woman at olegs and the option was avaliable. The only time I use a respec is to fix errors I made while making and leveling my character. I create characters to role play so the story decisions are normally important to me so going from a lawful good character to an evil one is a situation i would rather just roll a new avatar

She does so as 2.0.4, at least in new walkthrough.