Both games have all the DLC (bar the IKEA collection for TS2 from I believe).
Both games have the Denuvo DRM for some reason so keep that in mind if you're worried about it. Seems to be a false alarm, EA removed any mention of Denuvo from the store pages.
The Sims 1 will still run at its original resolution, but will now scale pixels to make better use of larger monitors while preserving the look and layout of the game.
Old save files and mods are compatible with this version of the game (TS for sure according to the help page, I'm not certain about TS2).
Edit: Yes, I could use Lutris to launch EA app and verify this game. I know it's lazy of me, but these little unnecessary barriers are annoying; I will just save my money and spend it on a game that opts to not use them like EA is wont to do. As the company can't help itself, as it is trying to emulate the success of Steam but falling on its face.
Happy The Sims 1 and The Sims 2 remaster day, regardless, as EA listened to The Sims community at least!