I am planning on making a mouse with 3 Omron switches, a Pixart PMW3320DB-TYDU and a scrollwheel from an old mouse but it's hard to find microcontrollers made for mice but I know Arduino's can be used but can I connect it to these things? Thanks!
Yeah, some people cannot find a good mouse.
You can try, if you are confident you understand programming and datasheet for the optical tracking part, well enough to write a library for it. Or you are lucky and find a library.
Beware that not all arduinos can be used to emulate (or implement) an USB mouse Keyboard - Arduino Reference
It looks like you have researched the parts carefully. Work one part at a time and good luck!