I've seen crosses of D. schizandra and prolifera. I have not seen other crosses. (I'm not sure if that cross is fertile and could cross with D. adelae).
I've always had some D. adelae plants and learned, for whoever asked it, that, yes, if you expose its roots to light, it will grow plantlets along it. Looks like D. schizandra does the same thing. I have not yet tried with my D. prolifera.
Regarding D. prolifera, I've learned that if you let the flower touch the live sphagnum it's growing in, preferably holding it down with a piece of sphagnum, it will sprout a new plantlet that will grow to near adult size within two-three months. I think I've had 100% success with this propagation method.
Typically, I keep my two Queensland sisters (I'm still looking for D. schizandra) in with my Neps., so they get the same fertilizer sprayed on their leaves as the Neps, but I make sure that they don't get any coffee treatment.