If you actually want a good multi-GPU system, just get an NVIDIA-designed system. There's no good reason to try to design and build one yourself when you will be relying almost entirely on NVIDIA cards and their multi-GPU communication.

I think the DGS Station only has a Single Blackwell GPU. Are there any other variants that has Multi-GPU that is not a Cluster or a Rack?

They aren't selling one yet for the Blackwell generation.