vertical 10 would be pmuch better suited for day geckos. any arboreal type animal would prefer the vertical design.
its pretty easy to do. Ben Green has a nice write up on his site and also sells the inserts.
http://www.chocohut.org/
as far as the 29 goes, i wouldnt run all water features off the same body of water. your misting water needs to be perfectly clear to avoind cloggin the nozzles. foggers are pretty sensative also, and need clean water. your recycled waterfall water wont be clean enough for either of these, IMO.
for filtration you could run an external canister filter. depending on how many fish, how much you feed, and well you plant the thing, you may not need any artificial filtration.
i wouldnt run an undergravel on a viv or paludarium though, because there is going to be a lot of silt creeated from the land substrate. you dont want that stuff gatering under an undergravel to rot.