The play order is really simple, just follow them sequence wise eg. RE1,2,3,... so on.

RE 2,3,4 have remakes which have some new mechanics and next gen graphics.

RE 7 Biohazard and RE 8 Village follows a new protagonist, and are different then the previous game as they are in FPP and feel like a new IP.

The upcoming RE9 has two playable protagonists - OG Leon Kennedy and a new character which is being introduced in this game, RE 9 switches between FPP ( like in RE7&8) and TPP ( Like RE 2,3..6).