Hi,
How cold will it be when the RV is in use (worst case)?
If you boondock electric heat won't be suitable.
If there will be shore power, I favor 1/2 size oil filled heaters that can be tucked away into otherwise wasted space. I've had all but three outlets upgraded to high quality female plugs.
There are heated carpets available. I managed to find some that have no wires, so they can be cut to shape. I chose indoor/outdoor carpet so I can pressure wash them if they become soiled.
Another way to add heating capacity is to run auxiliary shore power cords. I have added a 20 and 15 amp. This lets me heat 100% electrically if I have access to three shore power 15 amp circuits.
For propane heating, I'd suggest the Platinum Cat.
There are propane heaters that have through the wall chimney's.