What makes the game run the fastest?
Thank you for any help! :)
For a genre as undemanding as the visual novel, everything should work quickly, and only gross errors can get in your way.
There aren't hundreds of physics polygons or thousands of collision polygons here.
If you have backgrounds larger than 1920*1080 it is better to keep the backgrounds with different sprites. That it did not turn out that you loaded one background, but in the memory sits a lot of frames with other backgrounds that are not needed in this scene.
You can make two scenes for an example and show us the project file, we will help optimize.