the Steam Deck is pretty powerful, but it's still based on 2020 era x86 laptop hardware only gets about 1.9 teraflops, the Switch 2 is estimated to be 3.9 teraflops, which pretty much makes it a portable Series S if you think about it
These days it's almost impossible to be without a wall outlet for more than 3 hours unless you're planning a massive travel then you got decent power banks under $60 that can do 100ws now