Procedural Foliage Spawner unuseable in 5.3 & 5.4?!

I’m pretty sure I’ve used Procedural Volumes in the past projects without any issues.
Now it seems my Unreal Level File either gets corrupted so that I can no longer even open it again ( if I choose the wrong option in trying to increase the foliage growth) or it just turns things black and gets stuck?!

Could it be the size of my Landscape? I’m using these settings

I’m just trying to get this to look more full

I’m not sure which is the correct option to choose. These are the properties I’m altering

Here the foliage distribution is looking decent I guess but it’s lagging so much and I’ve only added one grass static mesh.

Here are the settings I used