ARM CPUs are significantly more power efficient than X86 CPUs.
It's true that this is a factor. I doubt it's that big though, mainly because I can't see the CPU block being the main power drain in a game console. So the difference in power draw due to CPU architecture seems as though it should be modest.
Who said Next Switch will be using Samsung 8N process?
The rumour mill. But from a performance/Watt point of view it is not too dissimilar from the process Mariko is already on (albeit twice as dense), and significantly worse than TSMC 7nm that Van Gogh uses. I can't really see it as a viable node for a Switch console, unless Nintendo got a low enough price per wafer that they could save money on it simply scaling Mariko. As Dampf points out, it's power characteristics makes it problematic for low power design, if you are looking at even modest increases in performance over Mariko.
Nintendo doesnt need TFlops. Advanced upscaling techniques are more usefull. So with Ampere they can render at 720p and even upscale to 2160 with DLSS-UP and get better image quality than render at 1080p without DLSS.
Not true. While DLSS is a low cost process on a discrete desktop GPU, its demands get problematic on low power devices. If, for example, you look at a desktop Ampere 3090 GPU, you need to divide its speed by 20 (to simulate 4SMs) and that still represents 15+W for the GPU alone (and you need to factor in CPU and memory in the 3W of Mariko) so you need to divide clocks by three or so to get anywhere close to where you need to be. And of course you still need time for the game logic to do its thing, and of course the rendering at the native resolution. No matter what I do, I can't get the numbers to fit when you take target SoC limitations into account. Not even close. (And given the nature of DLSS, all post processing would go after the DLSS step, at a full 4k.)
Now, I don't know to what extent a future Nintendo SoC could change the variables around. But in its present incarnation the approach is problematic within the Switch design constraints. Something more light weight is needed.
Basically, if you want to have a Switch that performs like a Steam Deck, you have to somehow reduce power draw by a factor of five. That's ... quite a challenge.