I know you guys will hate me for that but... Get a Mac. ;)
I used to use two different DAWs on the same laptop, sometimes I had them both running at once to quickly rebuild the mix I'd created one into the other, quickly comparing. Numerous times I inadvertently initiated playback in one while the other was already engaged. Both played simultaneously.
Admitting that you assign different outputs to those two apps, or that your hardware allows you to pick the headphone source, like a Focusrite Scarlett does, you accomplish exactly what you want. Just to be sure I am testing it right now, playing back one of my Logic projects one the studio monitors while I'm messing with the standalone version of Korg's MonoPoly in the headphones. Works A1, though I can't figure out why I'd want to do that...