https://wccftech.com/gta-trilogy-definitive-edition-runs-far-better-on-pc-by-enabling-dx12/

GTA Trilogy Definitive Edition is far from the perfect remaster Rockstar fans had dreamed of, between the performance issues on PC and next-gen platforms and the huge downtime caused to the Rockstar Games Launcher.

On PC, though, there is a way to improve the game's performance. YouTuber Joker Productions found that switching the game's API from the default DirectX 11 to DirectX 12 significantly boosted smoothness, mainly due to the more consistent frame timing. To do that, thanks to the underlying Unreal Engine tech, you just need to go into the Rockstar Games Launcher settings for each of the games in the collection and add -dx12 under launch arguments.