I have Windows7pro 64-bit and I can run all the JK series on my pc, just fyi. I have the original disc versions of course, so I can't say what may or may not work with the steam based versions. If there's a problem there, you should contact whoever is in charge on steam or whoever ported them for that format at LA.
Windows 7 Professional edition has the option to use a feature called "XP Mode." To use it however you need to download it from the microsoft site AND you have to install windows genuine advantage activation or whatever it's called. So if you can stomach that, you can get greater compatibility (for stuff that would work in XP that is). But I assure you that JK/Mots work here. The only problem I run into is that the loading/menu screens have the colors all distorted (or appear as solid black) UNLESS You run them in a window (so small menu screens in good color or else messed up in full screen). There are patches and hacks on jkhub.net that assist with this or you can use command lines to help out.
Some people give up on all this and just "keep around" an extra pc (or multiboot partition) with Windows 98SE on it for stuff like this. But whatever floats your boat...
For dos games like Dark Forces, I recommend DosBox to run the games at proper speed, with full sound and such. It's free and easy to use, highly recommended. However with DF1 specifically, there is the ongoing DarkXL project that might interest you. Check it out!
As for JK Enhanced, the last time I tried to run it I still had XPpro and 2000pro if I can recall, but I'm pretty sure it works on Vista/7 as well. I just haven't had time to try it. I don't see why it wouldn't... but you can try contacting the author of JKE or post on their forum at jkhub (though he hasn't updated in a long time).