SO I’ve done some more testing. Even if you don’t crash, you’ll get a vram limitation. It seems massive tilesets just can’t be imported. anything larger than 16k total just wouldn’t import with 32GB of ram and 10GB of vram. I had some luck merging the tileset in WM and importing as a single heightmap, ignoring the old UE4 knowledge that an 8k heightmap was the maximum, but it only enabled me to load a slightly larger total landscape.
Right now I’m testing a 32k 8x8 4033x4033 tileset, by converting from a world composition 4.27.2 project to a world partition project using level instances. I’m curious to see if world partition will work within each level instance. if it does, then it’ll result in being some bizarre hybrid of WC and WP. I’ll post back here with results.