I have one piece of Rotala sp 'mini' that I was given by accident that grows great in my tank with low to moderate lighting. I've been told that it needs more light than I have, but It seems to be doing well.
My caboma also "melted" but my hornwort is going absolutely bonkers... it's doing great.. so great I now understand why it's listed as an invasive plant
I ditched my hornwort because of its reputation to drop needles and make a mess.
In my RCS tank I keep wisteria, ludwigia, java moss, najas, hygro, dwarf sag, vals, etc..
The things that provide the best cover are java moss (for shrimplets) and wisteria which grows like mad. Honestly the shrimp love it all. I think I would also recommend dwarf sag.. still early on mine, but I think it'll grow in for some good low cover.