Expect it to be around the PS4 (probably bit below).
With DLSS for upscaleing though, it will play games slightly better than a base PS4.
(while consuming like ~20watts)
That roughly translates to about 4-5 times more powerfull than the current Switch.
I would not expect more than that (it depends on how big, heavy, and pricey nintendo want to go though).
(if its more powerfull than I expect, then its bound to be heavier, bigger, and more expensive as well)