Yeah, it's not exactly a technical show-piece. It's an indie game, a bit rough around the edges to put it lightly. My brother had a blast with it though... you just have to be willing to put up with a lot of jank. He seems to like quite a few jank games though, he's a big fan of Two Worlds as well.
As far as settings go, around E3 one of the dev's initially said it was coming to Xbox One X with "Epic Settings", but he didn't mention resolution. Another dev interviewd a few days later said "1080p 60fps w/ some PC only features.
It's probable that the person referring to Epic Settings was talking about the 1440p/30fps "Detail" mode. The person saying "Very High" Settings might even be referring to Epic settings, because as far as I know PC goes Low>Medium>High>Epic IIRC. Another point is that the dev's say they never mentioned 4k/60fps at all; my guess is some publications got all of these things mixed up.
Here are a few things they mentioned specifically about Xbox One X version:
-trueSKY advanced volumetrics (which isn't currently on any of the console versions)
-Higher resolution textures
-Higher resolution meshes
-Improved Lighting
-Smoother LOD loading
-No Host tethering distance regardless of clients console (in split-screen and non-dedicated, the game world fits into RAM/ only console with this feature)
Also worth noting the 1080p might be a dynamic resolution to keep framerate high, that was said months ago though and I'm not sure if that will still be the case at launch.