I know a few people on this forum that have talked to Bob (reptileuv) and he has told them that it is ok and there is no problem using the megaray at an angle. It doesn't affect the bulb nor the BD at all in a negative way, it's all the same effect when you use it vertically.
I would go for biggest enclousure that you can afford. I prefer ungrouted tile because you can remove it to clean if needed. Also if you want to change it out for something else, you can very easily. Good luck with your future dragon. Here is a pic of Luna's home. It is 4x2x2. I still need to do...
I would not keep more than 1 in a tank. Unless you can be there supervising them all the time, I have read too many horror stories about what happens when more than 1 beardie is housed together. I would not take the risk, but that is just my opionion.
It is 12-13" away from the basking rock and my temp are in 100-115 range. I thought I would have trouble with the temps being too high, but they are in the proper range. I have only been using the Megaray for 2 days, but so far I love it.
I got them from Lowes. They are 6x6 and cost I think .88 each. When she poos I just wipe it up with baby wipes. They are not grouted so I can remove them to clean if I have to. I really like them. The best part is they will last forever.