I found that increasing the “Loading Range” in WorldSettings , under the WorldPartition category.
With preview grids turned on, I could see the range it would load in a sphere underneath the camera.
This seems to be what will be loaded at runtime for player controlling the pawn.
I was able to find a nice middle ground using f8 (to detail the play-in-viewport so I could fly a camera around).
I haven’t tried with HLODs yet. But I think this was the issue; that that loading range was too small.
Though it seems like it would have loaded the landscape streaming proxy I was standing on regardless of the range. It meets my needs.