You can more powerful / faster GPUs in an Intel Mac Pro than the M2 Ultra GPU for sure.

I do recall a while back Nvidia did release updated MacOS drivers, but I’m not sure of the state of those on modern macOS.

But it certainly was possible to run an NVIDIA eGPU at some point.

Depends but no, only AMD cards are supported (in MacOS) for eGPU and they're all slow as hell too (for inference)