Currently I am trying to speedup my scene, with around 70k total meshes, 30k active meshes I get around 10 FPS. I am playing around with layer masking to decrease the number of active meshes since some of these meshes tend to lie over each other. After layer masking I get around 20k active meshes, however it seems as though for large scenes the FPS are roughly the same and intuitively I would assume that less active meshes means I should have achieved some kind of speedup. I get that with layer masking the instances are still present just not visible for the camera so I thought them not being visible = less rendering. Do the active meshes not have an impact on performance? Is there something else I can do instead of layer masking to avoid rendering meshes that are not actually visible due to being below another mesh or do they not get rendered anyhow?
Hello 
by “active” do you mean you used Mesh.isEnabled or Mesh.isVisible ?
I would be curious to see your 70k meshes scene, by the way 
Depending on the case, I would say there is a lot to discuss when it comes to optimization with a LOT of meshes… (LOD, SolidParticleSystem, etc…)
++
Tricotou
We have a dedicated page for it, you might find something there that will be helpful:
Optimizing Your Scene | Babylon.js Documentation (babylonjs.com)
With active I mean the number in the babylon inspector. In the performance viewer there is a metric called active meshes (truth be told im not sure what this refers to in terms of babylon properties).
Unfortunately it is a company related issue so I cant show it publicly sorry 
LOD we already have and it improved it a lot. Im not sure if a SolidParticleSystem would work since we still have to interact with the meshes by click.