how to remove completly an app

How to remove an app is depending on how it was installed.

For App Store apps, you can just move them to the trash from the applications folder.

For drag and drop apps you get on a disk image that you drag into the applications folder, you can again just drag those to the trash, an exception it is when you run it the first time and ask if you want to install something in that case see the next section.

For the above two methods, the only thing left behind will be your data created by the app, and that could include configuration files; however, none of those will cause any harm to your Mac.

For apps that use a package installer (cardboard box, icon), or the developer’s own installer, you’ll need to get an uninstaller or instructions from the developer on how to uninstall. If the developer doesn’t have instructions or an installer, you shouldn’t have installed it in the first place. You would then have to use some tool to find all the associated parts and remove them. The only parts that can continue to affect the system would be in a handful of folders in one of the Libraries.

For package installers, I use an app called Suspicious Package by Mother’s Ruin Software to view what the app is going to install and where. That could be used to find all the parts if it was a package installer.

The choice is yours.

I would be sure, have a Rescue Plan In-Place. This comprises having 3 Backups using 2 methods and 1 Off Site incase of Theft, Loss or Natural Disasters. A Time Machine Backup  is very useful, 

For addition purposes - two Tested Clones each to separate external drives. This is insurance incase the upgrades goes sideways. At least one Tested Clone and / or Time Machine Backup should be Off - Site

Does my CCC backup have to be bootable for me to restore data from it?

Good choice not to install and use the BrickMyMac aka CleanMyMac.

Usually, one of the better methods to use is via the Developers specific Instructions.

Some offer instructions, some offer an uninstalled that is built into the application and other may suggest reinstalling and then following their instructions to remove it.

There is an Application which is safe to use called Find Any File and follow their instruction on how best to use the application.

Then there is a suggested Uninstaller ( never used it personally ) called AppDelete