dark souls is like demons souls but with added mechanics and better boss fights, they get progressively better in the series, some say bloodborne, and some say sekiro are the hardest. dark souls 1 and 2 have a mechanic called poise where heavier armors allow you to tank blows from enemies and not get staggered, dark souls 3 takes a more demons souls approach with the removal of poise and giving certain weapons hyperarmor over others.

pvp in demons souls remake is fairly different compared to the original, mostly due to a lot of weapons not being able to stunlock anymore, though there are reliable ones still, and netcode is basically the same but front of the face backstabs happen less often (imo)