You may find only a single male will work but since females are the more colorful, you may be fine with that. You are doing a species tank with Metriaclima estherae? All orange or will you try to find Minos Reef to get the blue males?
I would not mix zebra species as Metriaclima callainos and Metriaclima estherae (for example) both being solid colored Metriaclima can be expected to fight and produce hybrids.
Snails are hit or miss from what I’ve heard, sometimes they do good, sometimes the mbunas will destroy them. Worth a shot though.
Also don’t worry about how fast the fish grow. Mbunas generally pack on an inch per month, slow down at about 3 inches. I got a 2 a week or two ago at an inch, one of them has at least a quarter inch. Zebras are a bit slower but still fast.
Snails can get out of hand quick. Maybe a singular snail would be good, but not snails plural. Plus, you already have the plec, so no need for snails besides the little cracks