Hi,
I heat 100% electrically at temperatures down to -36 C (-34 f).
My personal favorite is the radiant type. The safest is probably the oil filled type. Plan to upgrade the poor quality "stab" type outlets in the RV, or else avoid using the high setting.
I found some lovely 1/2 size oil filled that draw about 464 watts and tucked them into out of the way corners.
I use electric heated carpets, too.
Tank and pipe freeze up may be an issue. To solve that problem I replaced the return air grill for the furnace with a dual window fan.