I would only get 5 or 6 if you get the Peppered, Corydoras paleatus. If you decide on Corydoras panda, more would be OK, but 5 minimum. Or have both, 3 or 4 of each.
Be careful of your temperatures. Rams are mentioned, they need 82F. Both of these corys will fail at that heat.
Back to your initial question in post #1. The C. panda info on Seriously Fish mentions doing a biotope (sand, lots of branches, no plants) if you want to be authentic, or you can do a normal well-planted tank. The main thing is to have lots of surfaces for corys to hide under and browse, be they plant leaves, wood, etc. These fish are continual browsers, and the more surfaces the better.
And not bright light, so floating plants.
And corys geenerally off the substrate was mentioned. Almost all cory species will spend time browsing plant leaves, as mentioned above. Few remain on the substrate, though some do more than others. The dwarf species are mainly in the water column. Pandas do as well, and C. leucomelas and others.