I guess I"m not entirely sure of your concern. Do you have a pic of your tank you can post? If the concern is the puff being able to find a snail, no worries. Their eyes move independently like a chameleon, and they have terrific vision. Here's the most recent pics of my tank:
http://www.aquariacentral.com/forums/showthread.php?t=229255
Black substrate and about 75% filled with plants and drift wood. They can smell a snail as soon as I put it in, and will hunt it down with a vengeance. When I first started feeding them snails, I put in about 20 at once, thinking "that will last them for days". Nope. They systematically hunted down every last one until they looked like my uncle after thanksgiving dinner. They did everything but unbuckle their belts.
As far as specific decor, they really don't need much. The "heavily" planted/decorated thing is mainly important if you have more than one... that way they can hide and establish territories, etc. If you have one in a smallish tank, just make sure that the space is complex. If they have a bare space, they will get bored and spend their time buzzing up and down the glass. If you give them some stuff to swim around, and some caves/nooks/crannies to explore, they will spend their time playing and exploring.
You mentioned a concern about not being able to see them. You can see how my tank is planted, and I rarely have a problem counting all five at once. Most of the time, if I'm near the tank, they come right up to see what I'm doing. After a couple minutes (if they don't get food), they go back to playing/exploring.
HTH
