Apple knows exactly who the 2019/2023 Mac Pros are for - people who will pay for the best specs and need PCIe cards.
The 2019 was a very flexible machine, the 2023 is a lot less flexible. Don't expect that to change - the GPU and RAM will be staying on the SoC because that's the architecture every other Apple device has. You really wouldn't want to be in a world where the lowest selling Mac is the only one that still uses NUMA.
Apple hasn’t supported Nvidia for years. Those people already switched a long time ago. Apple silicon is rather competitive with AMD, especially with all that unified RAM.
If your GPU workflow is the classic kind of parallel processing with a compute bottleneck, then a couple of discrete GPUs is going to be faster, for sure.
If your GPU workflow is instead VRAM bottlenecked with unpredictable data access patterns then Apple silicon has the potential to be faster with that crazy amount of uRAM.
There’s also a dark tail of applications currently using the CPU because CPU-GPU-CPU latency is too damn high. Having everything on the same SoC will be a substantial latency improvement, which will enable using the GPU in places that discrete GPUs can’t go.
So if you’re doing 3D/vfx you’re probably unhappy, although as far as I know none of these people use Macs anyway, they all use PCs with high-end Nvidia cards.
On the other hand, this chip is going to be incredible for audio, once applications start taking advantage of it. Audio programming is really latency sensitive so discrete GPUs are right out, but with an SoC you can start to rely on the GPU being able to serve your request on time.
But at least the did supported eGPU on intel max - maybe not Cuda but metal, OpenGL, OpenCL. Now eGPU is gone as well in Apple silicon even though we latest MacBook Pro supports TB 4.0
The 2019 was a very flexible machine, the 2023 is a lot less flexible. Don't expect that to change - the GPU and RAM will be staying on the SoC because that's the architecture every other Apple device has. You really wouldn't want to be in a world where the lowest selling Mac is the only one that still uses NUMA.