How do I change image effects in-game?

I wish to change image effects in-game for people who have craptops (Like me) in CPU demanding games. Examples; Slender:The Arrival when you can change the texture detail, motion blur, shader quality, things like that. Another example is Among The Sleep, where you can change some things in-game, but I didn’t pay attention because it lagged like there was no tomorrow. Another example is Slender:Haunt, where you change the options at the main menu, like shadows, Screen Space Ambient Occlusion, things like that. Is there any way to do that? I’m only 13, so my javascript isn’t that great.

Since half th things you mentioned use the Unity Game Engine, it is obviously possible.

If you want to learn how to do it, you should look it up!