If you're asking if running the two concurrently works, I can't confirm that, but if you do a search you'll come up with some different ideas about running them concurrently. Here's one, but it's from '09 and I have no idea if it will work in TFF, although I don't see why not. And here's anotherfairly complete guide to doing this.
You use the separate Profile associated with each version from the Profile manager. Actually, now that I think about it, I ran into some problems with that when I tried doing it with TFF because the Profile manager was somehow broken there. Needed some work. But maybe they've gotten around to fixing that bug.
I got pretty involved with this for a while and then decided to abandon it, since I hardly use the G3, where I have TFF. Anyway, here's a thread at x704.net that, off and on, goes into this issue. MonkeyBoy seemed to have the best handle on it. You could always reopen that discussion, if you need some help with this.
I also raised it at the TFF forum, where I was trying to do this from the command line, which should be possible. But the TFF developer kind of let it hang in midstream, either because he didn't have the time, or because he just didn't know enough.
And maybe that Firefox Add-on I linked above, Profile Switcher, will simplify things.
I still think it's possible. And, while there may not have been that much at stake security wise between the 24, when it was first issued, and the 17, it's now up to 24.3.0, and I think as time goes by the security vulnerabilities will become more pronounced.
The profile manager thing looks interesting but I'll have to see if it extends to managing different versions of plugins.
Each Profile is self-contained and will have its own set of plug-ins, or lack of them.