Idk if there is an easy answer to this question but, Is there an optimum diff setting for 1 antminer L3+? Right now I have it set to 65536. Obviously I would like to know, with the hopes of maximizing my "mined last 24hr". Any insight on this would be appreciated 
Auto-diff should be fine. You may want to overclock your antminer (but I don't know it this still is possible without setting the whole thing on fire), but forcing any diff always resulted in lower payouts compared to auto-diff for me.