I don't have a lot of experience with Beauty Snakes. I do keep quite a few Gonyosoma, however, and a good friend of mine keeps quite a few of both.
For reference he keeps his Gonyosoma in cages that are 32" x 17" x 12". I would generally consider this to be a minimum for Gonyosoma. My specimens use floor area more than they use vertical area.
He's tried to keep E. taenuria in the same cages and felt they were much too small.
For whatever reason Gonyosoma do well in small cages. I don't necessarily recommend it, but they seem to do fine.
Beaty Snakes really seem to benefit from larger cages. There are some very experienced Beauty Snake keepers on this forum so I'll leave some bandwidth for them. I'm sure they'll recommend fairly large cages.