Your solution would cause the same issue im already having, except worse.
My foliage instances already have “query only” collision enabled so that I can do traces to interact with my foliage when needed. The foliage components cull method handles the culling a short distance from the player, no need for manual overlaps(which would likely cause a thermonuclear meltdown given how many foliage instances I have).
Mesh complexity isn’t the problem here and I’ve tested that by replacing all my foliage meshes with a single tri each like you suggested but no noticeable benefit.
Once the map is loaded everything works great with my trees being visible at all times and my undergrowth being culled a short distance from the player. FPS is good and stable. The problem im having is the load time at the beginning of the level is several hours which is obviously no good.
I wanted to have the trees on separate runtime grids from the undergrowth so I could load the undergrowth foliage in as I needed and not all at once at the start, but that won’t work because even loading a very small number of foliage instances in causes noticeable stutter due to the way unreal engine renders foliage instances. It does the same thing even when just trying to remove a couple of dozen instances at a time.
Disabling collision on my meshes all together seems to be the fix, getting me significant cuts to load time, which is one of the big reasons why grass types have such good performance.
For the moment it seems the best option is to try find a way to have collision on my undergrowth turned off initially and turn it back on when they’re close to the player.
EDIT: The problem is definitely the collision hulls that have to be generated when the map loads. When “query only” collision is enabled it takes hours to load, when collision is disabled it takes a couple of seconds to load. Need to find a good way of dynamically enabling and disabling collision close to the player without stutter. Hope this is of help to someone