Oil filled is the safest option. I would wake up at night worried if i had a ceramic heater in thereI do this often. However admittedly I should be using a small oil filled radiator or convection heater.
The small heater fan creates super dry air that's causes the plant to dry out extremely quickly. I always ensure my fan heater points away from the pots bland make sure the air can travel some distance before being reflected of the tent side walls.
Hope this helps
Ahhh if you don't live on the edge you take up too much room or so I'm toldSorry I can't offer any alternative just now but a million pleases be careful, have you an extinguisher?, some growing rooms can be fire hazards.