I don't know much about Bulbophyllum, but if you look them up on the Internet Orchid Species Photo Encyclopedia (IOSPE) Internet Orchid Species Photo Encyclopedia you can read about relative sizes.
One thing to remember is that a lot of Bulbophyllum grow in tight clusters, and a lot grow really long rhizomes between pseudobulbs, so they wander all over the place.
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All the other ones are on the medium to miniature side.
I don't know how large the snake you intend to put in the tank is, but I wouldn't put any heavy bodied snakes in there with many of the Bulbos you are asking about. The only one that might be sturdy enough would be Bulb sulawesii.