I'm trying to get the "perpendicular" picture here. You mean you will use the tanks horizontally (not make taller verticals out of them) in the normal position for an aquarium, but orient them with one side toward the wall? You could put them "back to back" this way, with the two backgrounds together, and the front viewing portion on either side, and still use the same lighting plan. Or you could stack them on two shelves or racks with room enough for regular aquarium reflector fluorescent lighting over each and orient them facing the room. Also, Petco has metal racks that will hold up to a 30 gallon on each level with room for a fluorescent reflector, or you might find something cheaper in Home Depot that's more adjustable for height. I have one of the Petco racks for a couple of tanks that works for me just fine, although the lower tank is just a bit tight for raising the hinged glass top.
What kind of top are you planning to use? I'm a proponent of the hinged glass lids with the plastic back-flaps that can be cut to admit any tubing or wiring from the rear, and generally fit tightly--although I've learned to also tape down the flap because frogs have been known to lift it and escape--See the recent discussions on cracks and space.
While lighting is important for your plants, especially if you have any of the blooming sort, or colorful bromeliads and want them to retain their color, the frogs don't really need much, as you obviously already know. One thing to keep in mind, is the farther away your lighting is, the less effective it is, but the closer, as with aquarium hoods resting right on the top, the more it will tend to heat up your tank. There always seems to be a trade-off somewhere.
-----
Patty
Pahsimeroi, Idaho
D. auratus blue
D. galactonotus pumpkin orange splash back
D. imitator
D. leucomelas
D. pumilio Bastimentos
D. fantasticus
P. terribilis mint and organe
D. reticulatus
D. castaneoticus
D. azureus
P vittatus
P. lugubris