Is my understanding correct that I may successfully graft pear to apple rootstock? Are pear rootstock prefered?
I wouldn't recommend it. I've grafted a couple of pear branches onto apple trees over the years, one lived for 7-8 years and even fruited, but the graft union looked terrible, it never did completely heal. There may be some compatible combinations possible, but I wouldn't think it worth your time to find them.
If you're looking for a "novelty act," Bartlett Pear on a Winter Banana Apple worked for me. Notice though, that's just not any apple, or rootstock. I'd read "that" combination was the only compatible pear - apple combo. There may be more, but I happened to have had "some of each," so I tried it. I removed the entire tree before it ever fruited... Winter Banana is nobody's favorite, and Bartlett's are everywhere!
And yes, Pear rootstock for Pears is defiantly "preferred."