Beautiful tanks, I would keep as a coral tank, the shallowness makes it creat for top down viewing, the overflow effect is being over rated. If the flow is smooth and steady not rushing the salt creep is minimal. Salt creep is from splashing water that dries up. If im viewing this correct it should collect in to collection chambers that flow into a sump like box then returned back up.
It depends on the interaction at the bottom where the water meets the collection. If it flows smoothly into the collection cup salt creep will be minimal. From the looks of it the water is a smooth sheet in order to not distort view.
WP isnt an issue since there are no seems. Although it may bow the support is actually spread over the entire curve instead of a 90 degree joint. Think of it like an oxygen tank, they use a single blank slab and for the piece to hold more pressure.
Algae would be the biggest problem, but i dont see why you couldn't do it with a normal sponge scrubber. Snails will survive as long as they having moving water over them. They only need to stay moist. Although they would take away from the look.
The price is too much and i doubt they would be very purposeful as a home system, however, if you own a business this would be a nice centerpiece in a lobby or such, although I would dread the thought of someone throwing a copper penny into it.