> "No indication for whether the CPU/GPU/RAM/SSD are upgradable or all soldered together on the board"
With 99.9% certainty this box is carrying on the legacy of the Deck and the Deck OLED, which means that it has a 100% custom crafted SoC with soldered components. Which also means they also could perform some trickery not found in "normal" PCs, like UDMA and custom interface.
> "but doesn't mention what kind of games it can run at that quality."
According to the specs it has a custom RDNA 3 chip w/ 28 CUs and boost clock at 2.45Ghz. The Playstation 5 has a custom RDNA 2 chip w/ 36 CUs @ 2.23 GHz and the Xbox Series X has a custom RDNA2 2 chip w/ 52 CUs @ 1.83Ghz.
Given the optimizations AMD made in RDNA 3 (the "budget" 9070XT can easily keep up with the prev gen "enthousiast" 9700XTX) I could make a safe bet it's on the same level of performance as a Playstation 5
> "No performance benchmarks, or mention of what the equivalent retail CPU/GPU to their custom one is."
~7600X, ~RX7700, but like I noted earlier that's meaningless because the overall architecture of the hardware in this box is likely completely incomparable with a generic PC (just like with XBX and PS5, by the way)