If you are gonna go buy-once, don't forget include a shroud in your plans. Of course you need one, but I mean get a matching (same marker is safest) one at the same time so you know it all fits, locks up reasonably well. Lanyards also are worth considering at the same time so it's all bought and set up from the get go.
I haven't used all these, can't vote usefully. With proper care (e.g. silicone or tapes to tighten it up) USGI surplus Norotos Rhino I mounts and J arms are fine and can be had super cheap. My favorite current mount is the Norotos TATM but again: have only used like 4-5 different ones and there are many more than that.
Many people insist the USGI GFRP J-arm is bad. I think it's fine, but do note that you flip the unit down FROM THE MOUNT. Don't grab the NOD and pull, but wrap your hand around the whole thing, with the index finger/thumb wrapped around the base of the mount. Grabbing the NOD (for max leverage) alone, you will eventually loosen the setup, or maybe snap off the J-Arm. Seen some broken ones, but that was also Marines so not unexpected
Also not explicitly looked at (implied in the options I think, but unclear) is the horn vs dovetail interface. Dovetails are neat but... have their own issues. I have Wilcox to Wilcox dovetail bits that also have two layers of electrical tape to tighten them up. Works for me as I do take them on and off a lot and it's an easier and more sure connect/disconnect but for yours... you probably rarely take it all apart. Really, there's no perfect solution I think.