I'm glad you like OD, I do too...to an extent.
Yep, purchasing gives you access to stable (not really, though) build of OD+ 1.9, also the beta through Stardock Central and alpha through Impulse. Be aware though, those are not any kind of build of 1.95, they are still 1.9. And therefore I won't say anything about 1.95 because it's literally nowhere to be seen.
In terms of waiting....hmmm, that's a tough one. And it's not being made by the fact that there is no clear idea of where things are going and/or what the roadmap is. Speculatively speaking, that information is not "ready for public consumption". Having used OD+ for almost 2 years, I'm guessing that by the looks of things any kind of stable new version is not likely to arrive this year. That's of course basing the assumption on the fact that it's not even on Coming Soon list on Stardock's site. In fact, it was there and then it was yanked off it faster than you can say Jack. So the ball is in your court now, a lot depends on your patience because you'll need shipping containers full of that with room to spare.
About compatibility...this one is easy as pie (cherry, preferably). Go here: OD product page
and click on the far right tab half way down the page called System Requirements. And you're done! As you can see so far only 32-bit OSes are officially supported by the stable build. Some people said here in forums that 64-bits works for them but if you wish to dip a toe in that pool you'll be on your own. Once again, your choice.