I don’t have a switch. From what I gather, the dock is just an USB C to HDMI dongle with extra USB ports, correct?

Does docked mode performance also trigger when an USB charging cable is plugged in? From what I gather the main issue why handheld mode is lower performance is the battery consumption.

If it does, does it then display 1080p@120hz on the integrated screen?

Nintendo does skew towards a younger audience though. Price and exlusive titles alone are much more compatible with a younger audience than e.g. the Steam Deck.