use foil bubble type roll insulation over all surfaces(include frame) the purpose of the over frame is thermal break.. Stops transfer through steel frame work to inside.
It's best to use the orange with the foil backing if you can afford it
Definitely spray foam. Then use reflectix too. Just an FYI, we are fulltimers...we coated the entire interior of our coach with reflectix...and for three years we've only used one 13,500 btu a/c unit all the way up to 104 degree weather. We also survived this past winter of -22F just fine in the coach. The plumbing bay? That's another story I don't even want to discuss.