Any suggestions on which unnecessary folders in my /user/~Library/ to exclude for backup? Using Backblaze for online backup. The below folders highlighted in blue in OmniDiskSweeper are what I'm thinking of excluding:
In my experience, a good backup app will automatically exclude the ~/Library/Caches folder. You can check whether it has the Apple-specified exclusion flag.
Here's another BackBlaze article on exclusions, which has several links: