They've got X actuation and Exact actuation now, but think it's just the Eagle types they aren't cross compatible. The MTB mechs don't have barrel adjusters though so you need to fit one somewhere in the cable run.
Plus you can end up with annoying cable routing situations like I have (X9 rear mech on Hook EXT-C), and I'm not totally convinced that my occasional front shift problems are not caused by the mega powerful spring in the rear mech. 10 speed sram mix n match is still the best though.
If only shimano had used the same pull ratio for mtb and road like sram so we could have just picked and matched instead of having to deal with grx.