Alrighty:
-fast-list helped a wee bit, but not a lot
--max-age can't use this due to backup schedule, if any file is missed it would corrupt other parts of the backup
--onedrive-delta --checkers 20 from this thread helped, but also not by a lot
client id via this method is depreciated as per Microsoft (need Enterprise or Azure subscription) 
So for kicks and giggles I installed v1.65.1 and boom, no authentication error and checking is quick again -- sync completed in 59 seconds (versus 2 hrs with v1.68.2) without any errors. Weird? I'm not sure I would call this 'solved' but definitely a band aid until this pops up again 