You could house 3 or 4 leucomelas in there. I've never kept Epipedobates so I wouldn't presume to advise you on them.
This is really personal preference. For terrarium plants you will need something in the daylight range (5000-10000K - I prefer 6700K). I like fluorescent bulbs, preferably T5, then perhaps T8. Alternatively, you can use CFL bulbs.
It depends on how much you have to heat it. If you have a false bottom, you can submerge an aquarium heater and use that to heat the whole terrarium. Alternatively, heat cables (like those sold for plants) are ideal. There are several variants - Hydor make the most well known (and most highly praised, to my knowledge).
I would say leucomelas.