Ysaye Heifetz....

I doubt if Heifetz would play excellent Ysaye's. As you rightly pointed out, the Ysaye's have widely varied styles and Heifetz I find has one style - his own. I would recommend recordings of Zhetmair, Rosand, Shumsky and Josefowicz.
Kremer's shows how effortless his technique is. His reminds one of Heifetz's style (which is atypical of Kremer), much more than Kavakos'.