Well, will look into the texture stuff, but about the performance. I have a few ideas but you’ll need to do some work. Prepare to get your hands dirty 
First, run profilegpu command and give me a screenshot of that, with the AHRVoxelization category expanded. Think the problem is there, cause I changed some stuff and now grids are twice as big as before, and on my tests it would seem that there’s a big drop after you reach a specific voxel count, but reaching that critical point depends on the bounds size.
After that, go to your bounds volume (not the post pro one, the one that you used to set the voxel size) , take a screenshot of the settings, interested in the size of the volume and the voxel size, increase the voxel size to the double, and run profilegpu again.
Also I have a feeling something is off, so bring the Ambient Intensity on the AHR settings down to zero, switch to Lighting Only, and take one or two screenshots. Also try increasing the initial displacement to 40 and take one or two screens again.
That should be enough for now.
On a side note, there’s a new option to make the bounds follow the camera, it has some flickering, but it should be really useful for open games. It’s on the AHR settings in the post pro volume, you have to tick Bounds Follow Camera and then tweak the Movable Bounds and Voxel Size (for you use the voxel size of the main post pro volume with all the others settings)