Hey-
I consider the Musconetcong River my home water, and I can certainly tell you that the set up of a prince nymph and/or a pheasant tail can certainly produce fish on that system.
I will say that it is a very caddis and stonefly heavy system, as well as bwo heavy in late spring, early summer where we are at now. You also see many midge hatches on that system on any given day. I fish the musconetcong 2-3 days a week, usually at the seasonal trout conservation area towards Mansfield, NJ. I fish this spot as it is about 5 minutes from where I live, and while it certainly sees a lot of pressure the majority of time they are well spread out within that stretch. You also can fish up or down from the section.
Late spring and early summer it is fished most heavily in the afternoon toward evenings when the hatches really pick up (other conditions aside), and people really hammer them on dry flies past the dead water up until the first big rapid. I have been lucky that I primarily fish tuesdays, wednesdays as they are my days off and I don't see that many people.
Those aren't bad flies by any means, but at this time be prepared with caddis pupas, stonefly nymphs (they still like a nice meal), bwo nymphs, emergers and dries, as well as midges. The Muskie midge is one specific pattern that comes to mind that works really well there, but any simplistic midge such as al's rat also works quite well. Late winter-early spring you see a very prolific stonefly hatch on this river, and it was quite extraordinary this year. It was one of the heaviest in recent memory.
I usually nymph with a sighter in a euro style, but this year I have done really well on dries alone, as well as dry dropper. Last week I caught several pushing 17" on a dry dropper with a bwo dry and a bwo emerger that I put floatant on.
If you would like to meet up one day I could certainly show you around some of the spots. You don't have a bad approach, I would just be willing to throw a lot more variation.