I have been reading a lot about these crabs lately and I have four in one of my tanks now. I'll share a few of my thoughts and discoveries here.
According to hobbyists in germany, red claw crabs don't require brackish water to live, only to breed. My experience is the same.
I have a straight freshwater tank and have seen successful molting and mating behaviours (the crab larvae all died but the adults seemed to enjoy trying).
Oddly, I have only seen one molted shell in my tank. I kept that one and dried it for future size comparisons and all the crabs are monsters compared to the size of the original shell. This size change proves that there has been molting going on in the last half year but I haven't seen the shells. Each crab has several burrows so I am not surprised that I haven't seen more shells.
It is a very rare occurence that I see all four crabs at the same time. Very rare. I had to take pictures and catalog their differences just to determine if I still actually had four crabs.
I don't see any evidence of them shredding my plants but I have seen them picking hornwort and eating it like it was a bunch of grapes. They spend a lot of time climbing around inside thick clusters of plants so they may be eating them, I just don't see it.
Aside from hornwort, I feed them fish flakes, algae wafers, zuchini, frozen bloodworms, betta pellets and I believe I also feed them Zebra Danios, Neon tetras and otocinclus catfish. I have no evidence of this, but I am missing fish. Truthfully, I don't feed them anything. They just get leftovers and aquarium table scraps.
They MUST have access to dry land. All of my crabs spend some of their day out of the water.
Here is a link to my attempt at cataloging my crabs:
I have crabs