Forepaw use multimeshinstance for multiple non moving meshes. reuse meshes and materials. DON'T USE THE GODOT DEFAULT MESHES, make your own and export it. the default meshes are for prototyping.
combine your non-moving meshes into a single supermesh. put your multiple colliders into single physics objects.
use alpha-Scisor whenever possible (if you don't need transparency). avoid using pure alpha.
make lights and decals small.
Godot doesn't have components
Forepaw glow effect on the whole scene
what else is active?
if you don't need PBR, change your materials to lambert or unshaded.
what is your PC? GPU and memory? Godot has greater requirements than unity, unity is said to work with 2Gb, godot requires at least 4. Godot is a more modern engine that takes advantage of Vulkan and GLES3, while unity's obsolete renderer was opengl-direct9, so also try changing to compatibility or mobile if your PC is too old.
also Godot is very different from unity (it's better) so something made for unity will need to be rethink-ed to make in Godot, since Godot uses nodes and scenes. This is a very common mistake of people migrating their entire games from unity. while you CAN change a few lines of code and get it to work, it will never work optimally.
