This got into the weeds but here's the basic rule:
Either PS2 3V or PS3 is fine. You will get better sounds (and possibly quilling whistle, depending on model) with PS3, but either will run reliably.
PS2 5V is a no go, unless you get it stupid cheap. It will randomly die at some point. If you can't swap to a PS32 board or do a TMCC upgrade to it on your own then pass on any PS2 5V locomotive that comes your way. You're looking at a ~$300 repair bill to have someone fix a dead PS2 5V locomotive for you.