Road cassette I’d use a road chain, they’re a smidgen (0.1mm actualy)narrower.
+1 for KMC, and I’m not sure they distinguish between road/mtb, which probably proves the narrowness is irelavent.
I still think 6 speed (or even fewer) would be better for DH than 10 speed. You’re going to be changing gears a lot with an 11-23. Just get an SLX 11-36 cassette, bin the biggest sprockets and fit a longer limit screw, fill the empty space on the freehub with singlespeed spacers. You’d still get 11-22, but you could shift it in 2 presses not 3-4.