I thought Linus's preview was decent. There was some cool comparisons with the Aya which was pretty interesting and sizes.. by golly thats one thicc boi.
There's also a hands-on from Toms Hardware - https://www.tomshardware.com/news/steam-deck-valve-hands-on
An interesting tidbit is they again re-iterated that the SSD is upgradable, and although a vague answer.. the guy doesn't make it sound too difficult to get to "Specifically, I wanted to know about upgradeability. Yes, they confirmed again, the SSD is slotted. Yes, you could get in there. "