i use places like g2a, and kinguin for xbox, but theres too many "account" sales, which are terrible, and you should never do.

for PS4, I just have a US account and buy most things of either amazon or psn (using gift cards purchased from amazon).

Well from looking online, I can see about $5 difference between the cheapest online codes and say MA or TWH so I guess I'll get a physical disk I can resell.

I've used CD Keys a few times, however typically just wait for official Xbox sales to rotate to a game I need (I have so many unplayed games so purchasing new games seems pointless)

I would never go physical disc anymore and have actually purchased digital versions of games I had on disc in order to avoid having to put a disc in when I wanted to play a game