Re: Dojo Floor
If there are any local dojo with the various kinds of floors you're considering, perhaps you could check them out. The feel of different mats is quite different, and you'll probably have a preference....
Visitors to our dojo often complain, sometimes loudly, about the tatami-on-sprung-floor mat. It certainly draws attention to any flaws in your ukemi, and some beginners (me, for one) find it very hard to learn to roll on it. We have a few portable gym mats for demos, and sometimes put them over the tatami when teaching beginners to roll.
Tatami without a sprung floor are, in my opinion, too bloody hard.
If I had to build my own dojo I'd be hard put to decide between sprung-tatami and stuffed-canvas; the tatami give me bruises on my shoulders and hips, and the canvas gives me wrenches in my toes and ankles. If there's a happy medium I have yet to experience it.