I had a quick growing girl and she outgrew the 10g tank when she was about 3 months old. I don't know how big your guy is but I'm guessing the 30 gallon may be a little large for him. Plus it may be a little more of a hassel keeping temps and humidity correct on the larger tank. I would imagine you would be ok with just the 20 gallon.

On the substrate I can't imagine your bp getting upset you got rid of the pretty wood for some simpler paper towels or newspaper, thats more your preference. You'll also be able to control the exact temperature because it's easy to measure the temp on top of a paper towel but with the substrate you are currently using you gotta worry some about digging under the wood. Long story short, you can switch to paper towlels or newspaper but like the other post said, give him a day or two to get used to it.