Re: oyo henka
I'm not sure about either of these in Saotome Sensei's perspective.
I am under the impression that oyo henka is "variations", i.e. the technique is a nikkyo but doesn't neccessarily resemble the basic version when getting to the application. I guess this could come from a more dynamic attack, since the added motion allows for different application.
I've not come across the term kumite geiko, but reads like fighting practice to me, which could indicate that uke is resisting more, i.e. fighting to stop the technique happening.
probably doesn't help at all.