Periodically, I go thorough a spate of housecleaning, usually just before of just after a major MacOS upgrade. My rule is if I can't remember what an app does or the last time I used it, it goes. Probably doesn't help performance, but it sure cuts down on the distractions and makes it easier to locate what I really need.
If you've never tried it, sort ~/Library/Preferences in list view and by Date Modified, and take a look at the bottom of the list, i.e. what was modified LEAST recently.
