My only experience modding was arma 2 dayz and dayz standalone server modding and some fs22 xml edits. Some stuff like the DEM came over easy (I did have to do some resizing on it). Ground foliage (grass, bushes, etc) I can't remember if I was able to bring that as I redid it anyway. Ground texture paint could not come over from what I was told. I was able to export the fields and reimport them but they were all messed up and I had to redo all or most of them. All of the trees had to be redone.
It's cumbersome or was for me as I didn't and hell still don't have the experience. If you work on it now get good at it and not much changes in the next version, it probably wont be to bad. The roads all came over but then I changed those, same with the waterplanes.