I’d prefer it if one character were human , but it’s not necessary; I’d be interested in some shifter-on-shifter action! ;)
If you are interested, I do knew of one book that somewhat fits the bill. It’s an FMM fantasy erotic romance series by A. H. Lee that begins with Incubus Caged. The incubus is a panther shifter. There’s only some oral while he’s in his panther form, no intercourse.