Anything the same size or larger than the shrimp will see the shrimp as potential food. Not that it's a bad thing - shrimp are excellent nutrition. When shrimp molt they become expecially vulnerable, and can make a meal for almost anything. (I'm a little worried myself because I found the molt from my bamboo shrimp, haven't seen him yet, and while he's twice the size of the betta, he could have still been dinner.)
You might want to buy a half dozen and see how they fare in your tanks. You'll never know until you try.
As for apple snails - no loaches, puffers, or anything that is a mollusk eater. Kuhli loaches, expecially the black variety, are okay. Snails will need fed their own diet of veggies and pellet foods - they can't survive on leftovers alone. They also need 2.5 gallons a piece, and create a lot of poo, so factor that into your cleaning schedule and your tank space.
This said, I have a bamboo shrimp, ghost shrimp, and three species of apple snails, and I love them more than my fish. (But don't tell my fish that!)
Edit: The bamboo shrimp is okay - he's out scrounging for food at the moment.