My white clouds and bettas are fine. They can handle it. lol
Anyways, in my experience, my bettas are fine with white clouds, zebra danios, livebearers (platies, mollies, swordtails, guppies, endlers), tetras (neons and black phantoms), kuhli loaches, ADFs, catfish (cories, otos, featherfins/snyos, bumblebee and raphael), siamese algae eaters, fiddler crabs, snails, shrimp, plecos (rubberlip, bristlenose, and clown), gouramis (dwarf and pearl), tiger barbs (slightly torn fins, I would not suggest these), and goldfish. Yes, I do have a sorority in with my goldfish. They get along perfectly fine and everyone is happy and thriving and I make sure that all needs are met.
Kuhli loaches, ottos, and platys have worked well for me without any problems. I've had two different bettas live with that combination (one female and one male, of course not in the same tank) and both of them did just fine. The male though, for some reason, always wanted to sleep right next to the platys and I think it freaked them out at first.
Anyways, RCS are peaceful and they're more towards herbivores than anything. They clean your tank really well and, if anything, will become a snack for the betta. My bettas are fine with them and I've never had problems.
Panda corys are my favorite betta tank mate in my sorority tanks. They are a blast so active and entertaining. I have never had a problem with them and sometimes my bettas will glass surf in formation with them.