With regards to RAM:
One of the worst decisions Nintendo could do is make a SKU that has more RAM because it means a number of their customers who purchased another model can't play a certain game. For example, if there's a "Switch 2 Pro" will 16gigs of RAM at $500 and a very popular game was developed for it, what about the majority of users who bought the base model at launch? or the Lite digital-only version at launch?
Nintendo knows what they're doing. Having multiple Switch 2 models available, starting with the base LCD model that will be released at launch, is the way to go instead of putting all of their eggs into this one "Super Switch" with 16gigs of RAM, OLED screen, and so-on that some families wouldn't be to afford.
There absolutely will be multiple SKU's just like the Switch, but the features that are different are non-essential. The primary differences between the Switch, Switch Lite, and Switch OLED, are the aforementioned OLED screen, storage space, and the physical size. That's it. The actual guts of the Switch including the RAM are the same so that it doesn't matter which model you have. You can still play whatever Nintendo game you want.
It will absolutely be the same with the Switch 2. All this is say that 12gigs of RAM is what the Switch 2 will have through its lifespan. I'm confident there will be Switch 2 OLED with 512gig of internal storage and a small Switch 2 Lite that's smaller and perhaps digital only, but they're not going to upgrade the RAM or anything that would mean players who own a different SKU will be unable to play a game they want.