You should have a little clearance on top - you will have to measure to see how much.
I don't worry too much about using the heating "feature". In the summer, it's not needed (by us). Fall and Spring are our favorite times for dry camping - no-hookup sites are readily available without reservation, and we don't need the A/C. If it gets that cold, the furnace is available. And in the Fall and Spring, we'll carry sleeping bags for backup against cold.
A good mattress topper has made all the difference in our 2014 Rockwood A122. We can actually sleep at night.
We can no longer store the pillows on the bed with the camper folded down, but I just put them on the dinette table. With just the mattress, there is enough space folded down for the topper to stay on the bed with a fitted sheet and light blanket.
Obviously, I may have more vertical clearance between bed and roof than you do - hence the measurement recommendation. But even if you have to store it separately, the sleep is so much improved over feeling the hard wood underneath that I would do it.
just my thoughts and experiences - yours may differ