How did my #godotengine tank game go from 10 FPS to 30 FPS on my potato machine (GTX 980)??
Sadly by switching from the Vulkan renderer to Direct x 12. It's super frustrating as I've spent months trying to get meager gains, and ultimately its a neglected driver that was the issue.
There was other optimizations which mattered of course, which I'll mention in replies, but nothing was as big a jump as this.