it's rare to find a live-bearer tank clean enough to house CRS,
so I must first congratulate you on your tank keeping skills
sorry to sound so "tough" but a forum like this gets new people
showing up almost daily with "what can I keep with that" questions.
it's hopeless to help them since we never really know their tanks,
and most fish compatibility is anecdotal, with few stead fast rule.
I can already tell you that half your potential tank inhabitants
will eat CRS fry (as well as their own fry) if given the chance.
so livebarers, and most dainios and tetras will eat fry, most small
fish will leave adults alone with cover plants and good feeding.
thinking what's typically sold in LPS, I would avoid getting any
gouramis or widemouth catfish, as they will even harass adults.
if your main focus is to make the CRS Fry feel comfortable, you
will notice RCS keepers hosting various other invertebrates, and
various small rasping mouth (oto) or small barbel mouth (cory) fish.
you will occasionally see other small fish that are CRS fry friendly,
but experiences vary widely due to tank conditions, cover, and
how well the tank is being fed. for example, one poster my write
his ember tetras don't eat fry, while another will say they do. so
it often boils down to tank scape and feeding, not the fish choice.
most with 2 tanks like us, keep the small tank invert only, and the large
for community fish. some occasionally leave adults in the large tanks,
then move only berried females to the small tank to save the shrimplets.