Perf on Android seems reasonable based on feedback, however you can't push it too hard. As per usual, I suggest experimenting.
It supports alpha on textures, in general 3DObject uses the C3 rendering SDK, so it has those limitations, I have requested some features to help us get around that, but we'll see if Scirra implements it.
For other texture maps, it is a similar situation, I did a request to Scirra so that I might be able to implement normal map, etc. still waiting on a response.
Happy deving!