Witcher 3 1440p High or 1080p Ultra?

So I've been playing Witcher 3 capped at 40fps on High (no Hairworks) @ 1080p for a few days now, but I'm noticing some pop-in on the shadows and foliage that I'm not super-annoyed with, but I'm wondering if getting 31-36fps instead of a locked 40 is a huge detriment to gameplay. (CDPR mentioned reducing the input lag in their engine, and I definitely can tell - it's much more responsive at lower framerates than other games.)

I tested 1440p DSR on High (no AA or Hairworks) and it runs about the same as Ultra (no Hairworks) @ 1080p: 32-36fps. Amazing that it's not much lower...

Just wanted to get some opinions on whether Ultra settings, a higher resolution, or 40+fps is the most desirable in this game?

Rig in sig.