The Shadow NFX is better for bowing (at least in my opinion) than the bridge wing pickups Rev solo II (never tried it) and Underwood.
The bridge wing pickups have a more direct sound sitting closer to the string. They may work better for plywood basses, since less of the body resonance gets to the pickup.
The Underwood may (!) cause phasing effects because of the two piezo elements, but some instruments need them to get the same amplification strength from each string. You have to try that. The Rev Solo II may sound a bit woodier.
I have a Shadow bridge wing pickup, but use it rather seldom. For me it is either the NFX, a Full Circle or a mic close to the top. For the Full Circle you need either adjusters installed to be replaced by the Full Circle or need to let a luthier install the Full Circle into your bridge (so you have adjusters after that). So you may need to make changes to your bridge to be able to use a Full Circle. (There are different threads for adjusters, so get the right version of the Full Circle if you already have adjusters.)
For larger bridge wing distances than pickup thickness, you may use some hardwood or paper shims so that the pickup sits in firm enougth but not too firm (then it sounds less good).
The Shadow NFX can be used with a single or both foils, so you can experiment what sounds better and if one foil is enough, you have a spare one (and the battery could be used about twice as long before empty).
You don't need a preamp for the NFX, because it has a impedance buffer (making the signal more loadable by low impedance inputs) built-in. But this is also the reason you need a battery all the time. (Holds for a long time as long as you remove the plug from the battery adapter after playing.)
The NFX is probably not the best one but not bad, not too expensive (at least in Europe) and solves a lot of problems for beginners. If you would like to pay at least twice as much, and have time for experiments, somebody may tell you you should get an Ehrlund, but you need at least some, maybe a lot of time, to get the good sound out of your bass with it. The NFX is simpler to handle, but also more limited because of that.
The passive bridge wing pickups will sound best with an external impedance buffer/preamp. They work without (i.e. if the battery of the preamp is empty), but with less good sound quality.
Bowing often sounds rather harsh with bridge wing pickups. You can adjust the EQ trying to compensate, but with mixed pizz/bowing (without the time for adjustments) one of them doesn't sound good.
The truth is you have to try it for your bass, playing style, kind of music etc., so better get a used one first (perhaps not a Rev Solo II if already sanded down), so you won't loss too much money if you need to sell it again later.
