From what I've experienced there's 3 different types of "crap there's juice in my mouth" and I'm not sure which is "spitback" if they all aren't at this point.
Crackling/popping happens with the fancy coils a lot but also with oversaturation. You'll get a nice hot drop of juice shooting at you sometimes and that's no fun. Curved drip tips help this as well as offset ones but that's more of a design on the mod thing.
Buildup/condensation is another, I've noticed a wide bore drip tip really helps with this and it's a big issue with my small bore ones. Which sucks because I like the small bore ones better in general but when this happens, arg.
Then there's the just drinking juice/gurgling where I'm not getting shot at with pops of hot liquid but just sucking up drops. Oversaturation of the wick being the big issue. Whether that is a vacuum loss in the system, old wick, too thin of juice, whatever. This is the one that vaping higher wattages has helped me with. If there's no problem with the system and it's just overly juicy cotton vaping higher wattages vaporizes that juice quicker. Alternatively thicker/higher VG juices so it slows down the wicking. If you were building on the RBA I'd say use less wick, but since they're premade... ehh? I've heard good things about the Atom gCoils (or something like that), maybe give those a try since you've tried everything else?
