If you don't know exactly what a plist is doing, the best thing is to leave it alone. Plists are preferences lists (hence "plist") written by applications as notes to themselves about how to run. They are text files, very small for the most part and represent zero threat to the operation of the system unless you muck with them without knowing what you are doing (hint, hint, hint, hint).
Some plists will recreate if you delete them, others will leave the application in limbo, uncertain of what to do or where to find things. Applications like Appcleaner will try to clean out plists, but because the naming of plists is entirely up to the application, it does an imperfect job.
I've been running OSX since 2008, never done a totally clean install, always restored what I had, and my entire Preferences folder is only 124 megabytes, tiny in today's world, so my best advice, and yes, I'm shouting:
LEAVE THE LIBRARY FOLDER ALONE.