I've tried the NZ strike indicator and I find it just takes too much maintenance compared to the ole' foam stick on- the NZ will sink on you after a number off roll casts, which in a small stream situation, sucks. I find you can move a foamy a bunch of times still and give it a pinch and it usually holds where you put it unless you cast really aggressively, and it's not gonna get waterlogged.
If you are fishing small water or spooky trout and worry about the surface disturbance, just rip in in half or even into 1/4 if using a small fly. It really doesn't hit the water hard at all in small sizes and good casts. The oval shaped ones from orvis work pretty well for this.
If your gonna use a foamy it really doesn't need to be big unless heavy fast water is sinking it, and even then, I think using a yarn or other alternative that will float as well as gonna create just as much or more of a disturbance.
I can't speak to the ease of adjustment over knotted leaders, but I imagine you could probably get a foamy to slip over a knot or two before it stops sticking, although I've never been able to pass one over a tippet ring. PS I love tippet rings and use them always- even then the foamy is my answer. I either put the indicator above or below my tippet ring depending on the minimum and maximum depth I'm gonna be fishing for a while- if u encounter water deeper or shallower than that, adjust the tippet (rare occasion if you know the water you are fishing). The foam strike indicator (usually cut down in 1/2 or 1/4) has always been a more practical option for me- less fussing around and trying to keep yarn floating and they aren't too expensive. $5-$10 a year isn't too outrageous for the convenience of it, if you need an indicator. I still prefer to nymph without one, but that just isn't practical a lot of times, at least for me.
I must note, if I was overhead casting more often than roll casting, I might prefer the NZ, if only for it's lack of either crimping your leader (thingamajobber) or being a pain to get off (stick on foamy in cold conditions). This is conjecture since I didn't give the NZs much of a chance past a weekend of using them till they sunk and inevitably switching back to the foamy. I would argue as long as it isn't landing harder than an NZ, then why not?
That's just me but give it a try if ya gotta use one! Hope that helps.