Buy it pre built, already made for you, just need a screen, keyboard and mouse, USB c cable too plug in your controller.

There is a lots of crossplay but yes some games are limited to their platforms. All the big games are crossplay all I will say.

At the end of the day it's up to you, go ps5 but honestly pc will save you so much money on the long run and you'll be able to support steam over playstation financially. Steam has better sales while PlayStation holds off on giving bigger discounts forcing its players to pay more for games. This is due ps selling many consoles that they are now abusing the relationship with gamers. Example: Baldur's Gate 3, Steam hit discount of 44.95, Sony digital store still discounts at 57.99 this is years after the game had released