I can't view the pic from my phone.
My second response got cut off when the metro hit the underground section.
I realized I didn't answer your question.
If you don't already have a bunch of equipment for 30" tanks that you are trying to keep cross compatible, I would go with the two 40b in a vertical arrangement. I would keep each on its own water loop so you can do the biotopes youre interested in. I say so because i get frustrated by the lack of depth to the standard 30" tanks, it is less pronounced in the 20l because of the reduced height, but it is apparent in the taller 29.
Personally I would go with a stand that has a cabinet on the bottom for your mechanicals, preferably two canisters. The closed doors will spare you from the air pump madness...
I would probably do an oversized shelf. I would keep it wide enough to have a four foot fixture hanging over each tank. I say this because hydroponics lights are in 24 and 48" standard lengths and can be found in the same t5ho 6700k or 10000k setups for cheaper than replacement bulbs marked for aquarium use. My 24" fixture does fill the 30" tank nicely, if you decide to go that direction.
Keep enough space above the bottom tank to perform service, including using nets at all four corners and scrapers, etc. I've been through all that having my tank on a shelf, and I can tell you it sucks. Also the added space will let you adjust fixture height for different light levels.
Visually you will be making a compromise by having two tanks, but not as bad as the viewing angles if you were to keep 3. Another argument for added space above the bottom tank: I like to be able to stand in front of my shelf and be able to look down into the back wall of the tank, just under the shelf above it. This allows me to view stems from above, and if you do any lillies you will have space to enjoy the flowers, but I do personally prefer open top tanks.
My situation is a little different because I already have a ton of equipment for 30" tanks that I don't really want to take a hit on and my wallet is starting to feel the weight of this hobby. I'm sure I'll be posting a bunch of questions, trying to get what I want and squirm out of the $$s, but like any project, it will be fraught with compromise.
Hope that helps!
Now that I read that, maybe that's what I'll do!!