1) It just updates the position of your mouse every frame. Without it enabled your mouse will still render at 60fps. There isn't really a reason to turn it off honestly unless it's causing issues, hence why it's enabled by default

2) The latest patch adds a config setting to cap crafting speed. By default it caps to the speed of 120fps max, but you can uncap it or cap it to 60fps speed in the config.

3) That's just a vanilla bug with frameskip off, like the faster crafting. It can be fixed too obviously, but it's not as high a priority since it doesn't affect gameplay at all.

ty for the answers. Also, I just want to let you know, the mushroom trees like to flicker a lot with frame skip off, regardless of the mod on. Idk if you knew about this already but just an fyi ;3