I'd go with a thicker vapor barrier purely because you get exactly one try to get it right.
Very wise move to go with dehumidifier(s) installed along with your HVAC system. We've also had a wonderful experience with closed cell foam insulation.
Your garage will probably be fine with whatever coating you want to use since it will be new concrete, uncontaminated by petroleum products. With older concrete I've had great success with VCT (vinyl tiles). They can be damaged by point loads like jackstands though. Now is the perfect opportunity to make plans for lifts.
