Skyrim 2020 is a sprawling mass of meshes and textures, still under rapid evolution, but it makes for a very high-quality base layer that makes many other landscape, city, and clutter mods redundant.
Skyrim 2020 Parallax by Pfuscher at Skyrim Special Edition Nexus - Mods and Community (nexusmods.com)
It definitely keeps to a vanilla-plus aesthetic but in a photo-realistic way.
On the down side, it takes up a lot of disk space, and depending on whether you load the 2k, 4k, or 8k version, can be a resource hog. (I'm closer to "minimum" than "recommended" specs relative to the guide, so I'll probably downgrade to the 4k).
I'm troubleshooting my first pass through the Step guide but wasn't willing to do without 2020. So far they seem to be playing well enough together but it's a lot of surface area to look at.
The areas where I tend to run into conflicts that aren't automatically solved by default load order is some city replacers and JK's Skyrim.
I would recommend testing 2020 as a potential base layer for the next version of the guide, but with the assumption that it will be a time consuming process.