Iíve always used ceramics, having just just set up a new 4x2x2 I have used 1 75w radiator and it gets up to temperature (29c) no problem then runs at near 0% and up about 20% (Iíve got a Habistat digital dimming stat) power to maintain the temperature.
If 1 radiator isnít enough to heat the space you could always use 2.
The guards are an issue, everyone has sold out, I found 1 shop in France but they donít deliver to th UK.
This company https://www.aianos.co.uk
can make bespoke guards but their minimum charge is £35 + vat and postage (£20), so about the same as the radiator.
I would definitely recommend a radiator (or 2 if needed) as its low profile so canít be seen, can keep a larger space warmer on a lower wattage and more specifically for a BRB it keeps the humidity up, unlike lamps which normally dry the vivarium out.