I don't know what would be an acceptable fee, to be honest. In theory, 1 sat/byte (or maybe even 0!) would work, although I've seen signs that at least some miners might be setting their max block sizes to 2MB for now in order to squeeze some extra fees out of people. Anyway, I'm pretty sure Bcash can handle RBF. You could always start at 1 sat/byte and bump it up if it fails to confirm in a reasonable length of time.