What is the best maintenance software for my Mac?

None. Mac OS is self-maintaining, everything you need is built into the OS. It runs maintenance scripts automatically in the background. No Anti-Virus software or so-called “cleaning” apps are needed or recommended for Mac OS. They can conflict with Mac's own built-in security. At best they will slow your Mac by using unnecessary resources and at worst will bork your entire system. Your Mac has all the built-in protection you need.

I second none. macOS is the best and does not require any help from third party junk ware.