Has anyone had bad experiences with McAfee?

Just about anyone that has run it, or any other (so-called) anti-virus application on a Mac over the last couple of decades. See the other post here by BobTheFisherman.

Only that is junk software that is not needed except for a trash can.

Do not install third party apps that claim to clean, protect, boost performance, etc.

macOS - Security - Apple

Set up your Mac to be secure - Apple Support

Protect your Mac from malware - Apple Support

https://discussions.apple.com/docs/DOC-8841