There are a lot of ways it can work so it’s hard to guess. Group edge is the least clunky though if they all feed to the same pool is it also capped at 7? Because they could hit that fast without trying. The boss mob might get crazy powerful if 4 goons feed it edge every turn. Which I actually like if it’s not too overwhelming. I haven’t felt like I could do a boss mob without just making a unbeatable spirit or something for a couple editions.
I think capping it at 7 would still work, as there's really no reason to horde Edge, unless there are some ways to spend it that cost more than 7.
Grunt groups should limit ridiculous Edge gain for NPCs, just by reducing their action economy. Not to mention that, as Chandra points out, goons are generally going to be inferior to PCs, so they're likely not going to be as efficient at generating Edge. Also, if the boss is the one spending the whole pool, the goons are just going to drop that much quicker. Generally speaking, of course.
The QSR doesn't follow CRB rules anyway: You'll see that for example the Ancients got 0 Edge. It also doesn't touch on Professionality Rating. Detailed grunt rules were apparently left out for easiness in the Beginner Box, which is exactly why you can't depend on the QSR for a full SR6 CRB impression: It simplifies some things.
Okay, but if I'm doing prep to run a QSR game tomorrow, the CRB having the full set of rules and being available soonish doesn't really matter much, because I can only GM with what I have access to now.
And I get that it's probably frustrating for you guys to know the answers to all these questions and have to keep it to yourselves because of the NDA, but for those of us on the other side of the fence, all we can do is discuss and speculate until the CRB is available.