as far as the foam, i like to use the GE expanding foam. walmart sells it in their paint dept. i have used almost all of the others and the GE is my favorite so far. it cures white vs. yellow and cures with smaller air bubbles, making carving things out of it a bit easier.

i wrote this build journals as a sort of a tutorial, maybe it might help you out, maybe not...lol
http://www.frogforum.net/vivarium-te...aludarium.html

you can most definitely use a false bottom with live plants. the only downside to a false bottom is that you lose vertical space, but it does offer numerous advantages like a reservoir that you can filter, and since there is a reservoir of water, you can utilize a standard aquarium heater to heat the water, which, in turn, heats the air above it and creates a bit of humidity.

there is no specific procedure for carving water falls and such, it's just basically allow the foam to fully cure (about 48 hours) and then carve away. the water area would need to be sealed afterwards, but that is a whole other discussion

between the links pettios and i have provided, you should have enough to get you started. if you have any other questions, just feel free to ask.