Realize the Lexus RC lineup first came out for 2015 model year and that particular one you are looking at has a 2.0L turbocharged I4 (with both port and direct injection).  Not sure how many miles you need the vehicle to last you, but the long term reliability on that engine is still unknown.  That engine will be more complex than the naturally aspirated versions (3.5L V6) also offered on the RC.  As an example, it has 3 thermostats!   Otherwise, the RC has been pretty solid - as the saying goes you can always do worse when it comes to vehicles in this class (2-door sports luxury coupes).  That being said, if you can swing it, I would recommend the true and tried 3.5L naturally aspirated V6 engine for longevity and potential for fewer issues during the ownership period.

Dealer certification doesn't mean much. It needs to be inspected by somebody who isn't trying to sell it to you.

It could be. Make sure to have a mechanic inspect it.