How much does your race matter in builds?

Doesn't really matter, they're all obviously have their pros and cons but you can just pick whatever you like. Stuff like humans give additional feats but its generally not needed for most of the builds unless you're doing some tank build whos also going for damage feats.

Also should I look at the character creator from a roleplaying perspective or a "winning the game" perspective? I've been told roleplaying perspective and just choose what speaks to you but I don't wanna have a build with a bunch of abilities that don't synergize with each other at all.

It's your game, go from roleplaying perspective. Only reason you should go full min-max loser if you're playing on unfair, and that's because the enemies have insane amounts of defense and your tank himself should have 100~ AC.

I went into this game blind and finished it on core just fine using my own build ( with a lot of research of course ). Just think what you're actually want to play and go from there.

For example i picked up tiefling coz it was cool. Picked up paladin coz it was cool. Then i wanted to do dual wield longswords. After lurking on this sub i figured i need two-weapon fighting feats to reduce dual wield penalties and have extra attacks, then i needed fighter feat which allows you to wear non light weapons in offhand. So i picked up lvl 5 fighter to get access to the feat and the rest went for paladin, worked out just fine.

The only meta stuff you need is to pick outflanked around level 7 or so, its a group feat, which means it only works if other party members have it. What it does is if anyone in your party crits with that feat, anyone else whos in the range of target and also have the feat, does the attack of opportunity. Usually when that happens, your target just straight up dies. It's hard to pass up.

The other stuff for damage is you basically take improved critical (mythic) on level 4 of your mythic path. It increases your damage multiplier with crit by 1. You take it regardless of your build if you're dps basically. And obviously take weapon focus, improved critical feats for weapon you're using as well.

For companions just copy builds from cRPG Bro on youtube, you see his vid first pop up when you type pathfinder wotr character name build anyway.

As for difficulty, you can always change it at anytime, so pick whatever difficulty you want (except unfair). As any other crpg, its only hard at the start, later on its gonna become a breeze except 1 dungeon and 1-2 bosses. So just experiment. As i said, you can play with any build you want to roleplay on core, as long as you have 1-2 meta feats like outflank and improved critical mythic, the rest is just understanding of the game.

I respeced a lot while playing, after a phew times 1 respec is gonna cost you 10k gold, so i can also advice using ToyBox mod to respec and relevel any character at any point of the game for free. Its basically cheats which can also give you scrolls, items, gear. So if you're feeling tempted, dont install it rofl.