Sorry for the necrobump, just wanted to bring a bit of "closure" to this topic.
Ended up going for the frontrunner I mentioned in the OP (
LG UltraGear 34GP83A-B) . It was $140(ish) off during Prime Day so I jumped on it.
It's a 34" curved 3440x1440, IPS, 1ms, HDR ultrawide. FreeSync and G-Sync compatible.
And, uhh....
Holy shit. Coming from a 27" TN panel with no HDR, this new screen is... it's kind of overwhelming, actually. And this is just with factory settings, I haven't even bothered to calibrate it yet.
Many, many thanks to the various members who provided suggestions! Appreciate the feedback. That Alienware ultrawide OLED seems great, but this LG monitor is about 1/2 the price of that one (well, on the sale price that I bought it, that is), and was actually available when I wanted it. So maybe in a couple of years I'll revisit the OLED option.