I feel so confused.... (heat, light etc. No hoggie here yet so no hoggie in danger)

I have only terrarium pets so far, that are fine with my 20-21°Celsius in the room. Okay the found (not planned for) mourning geckos have my old table lamp close by so part of their terra is 23-24°Celsius.... (I want to upgrade that to a real heatlamp too one day)

But for a real heat lamp how even go about this? How to know what is the right "size" of heat lamp for the enclosure? And I've seen them just plopped on top of the terrarium mesh-lid. But will it not heat up that too much?? So does it really go on top without bringt a fire hazard or do holes have to be drilled? I don't have anything to drill holes into a metal mesh top or glass...

Do they have heat and uvb? Or is that always two different things? And for at night...there should be no light so light and heat has to be 2 things, right?

And a thermostat seems to be a must have too? That would need another drilled hole I guess....

I read and read and read... and understand nothing it feels like.

😞