Funny you mentioned Onyx. I do use it, and it's what prompted my asking about Safe Mode. Onyx's maintenance lists a bunch of caches and other items to be cleaned, and I was wondering if Onyx duplicates the items that Safe Mode cleans.
My only problem with Onyx is that when it restarts automatically, 1Password does not work in Safari until I shut down the iMac and reboot again. I've tried a manual restart, and just closing and reopening Safari, all for naught. Is there an Onyx setting I missed that's causing this to happen?
My hunch would be the issue would be specific to browser history, cache, etc., and you might try NOT deleting browser cache in Onyx, unless you have a problem to solve.
I would expect Onyx would be deleting the caches that are safe, and global, same as Safe Mode, and some other tools do. But again, just an educated guess, never dug up the differences.
Technically any and all cache is safe to delete by design, at least with regard to stability and user specific saved data. Cached info is simply remembered info, which is faster to load that finding and reloading the original data, or rechecking, validating, or just reading the original....particularly on hard drives.
It does get a little tricky around browsers that typically will cache as much as possible to increase speed. Clearing the cache means reloading the original information, and that may including loading pages from scratch, as well as re-calculating stuff like like screen position monitor size, etc. It all adds a little time. I expect is varies a bit by browser, and even to some degree by the version.