Treat them about the same as red-eye tree frogs and you should do well. They get just a little bit bigger than RETFs and as long as you keep to similar sized individuals should be able to communally house them with RETFs. This species from my understanding typically in the wild spends a lot of time inside deep plants and old hollow trees and they need water filled hollow trees in which to breed. So for my setup the only thing I have varied from my RETFs setup is I put an empty 3" plastic plant pot to mimic a tree 'hollow' and stuck the fake silk plants down in that rather than just in the substrate. Some days the milky is hiding out inside, sometimes outside, sometimes in plain site or under the silk leaves, and sometimes on the ground..so he's having fun exploring that's for sure.
I have been told that milkys are getting more popular (& prices are much lower this year - almost by half) because a couple people in the US have finally gotten successful breedings whereas they were being brought in through european breeders originally. I've been told they are fairly hardy much like gray treefrogs (where they can go short periods without a lot of humidity), but being my first time with them, I prefer treating them a bit more cautiously than my grays. I originally purchased a pair last month, but the stress of the show, drive, new habitat and all I think led to the death of the smaller one. I'm still debating on whether or not to house the remaining milky with my RETF later on (right now I can't cause the RETF is half the size of the milky).
One thing for sure...they love to jump AT you and hang on 
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PHWyvern