Depends what you want to do and which cards you have, but usually going with any older (3rd gen+) threadripper pro setup will give you a lot of pcie lanes.
I myself run with gigabyte trx40 aorus xtreme, but since it's regular threadripper (not pro) with 4 GPUs 2 of them will run at x16 and two of them at x8 speeds
I wonder why using 2 PSUs resulted in having slower interconnect.
There is no specs in this blogpost regarding cpu/motherboard choice, but if you go with threadripper pro they have 128 pci-e lanes for some time now, so using all GPUs at full speed shouldn't be a problem
Not sure why they stopped using 6 GPUs in thei builds - with 4 GPUs, both 9070 and rtx6000 come in 2 slot designs, so it easy to build it yourself using a bit more expensive, but still fairly regular motherboard.
With 6 GPUs you have to deal with risers, pcie retimers, dual PSUs and custom case for so value proposition there was much better IMO
I hope not.
Projects like that to have any chance at surviving have to be good phones first. Adding modularity will make it worse in terms of specs, more expensive and in the result dead on arrival.
Once they launch a few successful (or at least sustainable) products, they can maybe try doing some modularity
Quest pro: 1800 x 1920 pixels per eye, so ~3.5Mpx per eye
Vision pro: "The custom micro‑OLED display system features 23 million pixels"
So 11.5Mpix per eye, assuming similar aspect ratio (1:1) resolution ~3400x3400
Probably there is more then resolution to this, but still, seems impressive
Tesla uses something like 15kWh per 100km, so 5 mile drive is something like 1.1kWh