The Mac Studio is Apple’s realization that the best Mac Pro was actually the Mac mini with some slight modifications.
To be honest though, my usage does not benefit from the speed. The only benefit is to the reptile part of my brain that says “speed. Must have the fastest possible, and since I’m paying for it, even though maybe I should downgrade it, I want my speed.”
Then, like you said, on the WAN side you’ve got the monthly internet bill.
1Gbps is the sweet spot, especially since 6Ghz WiFi runs at something like 600Mbps in the real world a reasonable distance away from the WiFi router in an ideal deployment. Saturate your wired, and you get a slight benefit over a 500Mbps plan for your wireless.