I have 2 apple snails (same as mystery snails, I think) with 4 young senegals in planted 80gal. No problem, even the snails' tentacles (or whatever its name in English is) are fine.
My large ornatipinnis ate snails: Smaller ones where crushed in his jaws, larger ones, like applesnails where just turned out of their shell, like a croc rolling.
My endlicheris, senegalus and delhezi do not attack them at all.
I have three Golden Apple Snails in my setup, never been bothered by my Bichirs, My Apple snails are constantly laying eggs in the hood of my tank, Great things to have Go Buy Some!