In case you didn't know: Firestorm 7.1.9 has been released yesterday. It's the first release that supports PBR (Physically-Based Rendering).
https://www.firestormviewer.org/firestorm-gets-physical-fo...
On the one hand, this means that the Advanced Lighting Model is now permanently on. You can't turn it off again.
On the other hand, Firestorm supports multi-threading now. Firestorm 6 and earlier only ever used one CPU thread. Firestorm 7 can use all of them.
So all fearmongering that you'll need a high-end gaming rig for Firestorm 7 is just that, fearmongering. Unless you've got an absolute toaster that was already built as an absolute toaster, and that has never been powerful enough for virtual worlds, unless you have to turn everything off from transparent water to shaders to light sources, chances are Firestorm 7 will actually be faster than Firestorm 6.
To give you an example: I have a Ryzen 5 3600X, 16GB RAM and a Radeon RX590 graphics card with 8GB VRAM. This is nowhere near high-end.
What Firestorm 6 renders with 20-30fps with ambient occlusion and shadows off, Firestorm 7 may render with 50+fps with ambient occlusion and shadows on.