Hrmm I have had absolutely no issues of my betta hassling my cories (4 pandas). I think the true issue may be the size of the tank tbh. Mine are in the 14g that is about 18 inches tall so there is plenty of "head" space. I have no set routine to which I feed first. Cories do much much better in small groups. I originally just had the 2 pandas and while they moved about they were fairly listless. I added 2 more and its fairly rare to see them being slow or still for long now.
Other aquatic creatures: ELB-guppy hybrids, Corydoras panda, Scleromystax barbatus, harlequin rasboras, mollies, nerite snails, ghost shrimp