1080p on such a small screen is pointless, but if you're into that by the price of one Nintendo game you can upgrade your steam deck screen https://www.deckhd.com/
120Hz is not that different from the decks 90Hz screen, although if you chose to do the upgrade above that downgrades you to 60.
Mouse mode, not sure what that is, but the deck has the best of it's kind mouse emulation so I think it will be hard for the switch to compete.
Plus I get to keep my games, and whenever the SD2 comes out I'll get to keep my games and not have to buy them again.