I have a 21:9 with HDR (but only basic DisplayHDR 400-level), and I’m really enjoying the HDR as much as the extra pixels at the side even though the darks aren’t as good as the brights, and the brights aren’t as bright as a better set could provide.
If you specifically are interested in a good HDR picture, I would recommend you optimize for that. But keep in mind that HDR complicates screenshots, screen recordings, and broadcasting so if that’s a thing… beware 