I'm not sure if this is why everyone's experiencing lag, but this is how I fixed it:
1. Get into Windows settings
2. Click on System and stay on the display tab
3. Go down til you see "Graphics settings" and click on it
4. Click on the browse button under "Desktop app"
5. Search up "C:\Program Files (x86)\Steam\steamapps\common\SonicOrigins\build\main\projects\exec" in the bar at the top and click on Sonic Origins
6. Now click on "Sonic Origins" which is now under the browse button and click on "Options"
7. Select "High performance" as your graphics preference and save
8. Go play the game now, the lag should be fixed and now you should have fun :)

(now all we need to do is wait for music replacement mods for Sonic 3&K)