As was reported, the Steam Deck OLED comes with SteamOS 3.5 preinstalled, while the stable channel is still on 3.4.
This means if reviewers didn’t take care to properly match the software versions on the OLED and LCD models, they might not compare apples to apples. The effect is probably small, but so is the reported performance and power draw difference between the models. Also SteamOS 3.5 introduces the saturation slider which in its default setting tries to emulate sRGB more, and could affect screen comparisons.
See for example Taki Udon’s first video, where clearly it is visible that MangoHUD is an older version on the LCD model https://youtu.be/3C6ekDyO18s?t=807
So unless it is explicitly mentioned or shown otherwise, assume that part of the differences might be due to different software versions.
To be safe - yes. Presuming you’re talking about the SSD inside the Deck and not an external drive, that’s where the operating system is kept!
Theoretically you could move it and then update. But just in case there are drivers or settings on 3.5 that the OLED needs you should do it before moving it. It’s a tiny risk, but since it’s the same amount of work (just in a slightly different order) there’s no reason not to update before moving the drive.
Is it that simple? Just popping in the SSD from my old deck in the new deck and play?