I am planning a trip from GVA to SFO with UA/CO beginning of next year. The best prices and best connection times are via IAD or EWR

Having read through this post, I presume I should arrive into C gates and leave from C or D gates, Is 1h - 1h30 enough time to clear immigration and recheck my bags as to my understanding this will have to be done in IAD and not in SFO?

Or am I completely nuts and I should try and go for a later flight? or connect via EWR?

Thanks