Will your PC still be safe if you use the lowest sandbox setting?

I was wondering what those settings were for. If I set it as partially limited wouldn’t i still be able to just click clear sandbox contents if a program is bad?

No, resetting the sandboxed only removes apps sandboxed as fully virtualized. Apps sandboxed as Partially Limited are run on the real computer and thus can drop files, and make certain changes, to the real computer.

Also, partially limited is vulnerable to some variants of ransomware.