I've spent a lot of time in there. The area is pretty cool, lotsa wildlife and it's a real-deal wilderness environment.
Headnets - yes, but by that time of year (late july) things are calming down a bit. The most horrendous mosquitos i've ever seen in the lower 48 were around there. THe mountain passes are much less of a bug "hell" than along the river.
Also - the park service requires you camp in designated camp sites. Now, that said - "stealth" camping where you need to would be really easy around there. It can be really hard to plan on where you're gunna end up when hiking a long trip.
Now, I'm not giving any advice here (y'know, the leagal thing) BUT, get a permit, make your best guess as to a campsite and have that written on the piece of paper. If you don't actually camp at the exact site they want you in - (MAYBE) you'll be asked by a ranger (MAYBE) you saw grizzly tracks near the campsite and (MAYBE) you chose not to camp there and (maybe) thats what you can tell the backcountry ranger, who is most probably really nice and won't even ask.
The camping zones are NOT an issue outside the park boundary.
and - Take bear spray.