I've not had neons before so can't comment on whether they'd be ok with a SFF , but i vaguely remember that they might be fin nippers and bettas (SFF) are slow with long flowy fins. Maybe someone else can confirm that.
How much current is in your tank?, they do prefer a slower current but plants and hdiey places can help offset it. But some even like playing in the filter outlet - mine did.
I kept my male betta with platy and a whiptail without problems. Me female betta is in the community tank with all sorts.