Hello, my friend just bought the game and we want to play together as questing, PVE and more. My question is should he pick a race from my alliance or not and WHY ?
If you both plan to do PvP together in future yes he needs to be the same faction (alliance) as you.
If he gets a pre-order code or buys the explorers back from the Crown Store he can choose any race in any alliance.
If you both plan to never PvP then your faction won't matter past where it places you both in the world after the tutorial (each faction has a starting island they will be placed on, but you can just quick travel to one another to go to wherever you want to both start)
If you want a pre-order code to apply to his account I have one spare, I can't guarantee it still works as I have offered it out a few times now, but each person said they never used it.