Super Mario Odyssey’s handheld resolution will run at 720p and 60fps, while the current build of the docked version has been bumped up to 900p (up from 720p at the E3 demo). This matches the development seen with Splatoon 2, where early version ran at 720p while docked before dynamic resolution scaling was added in later development. This demonstrates that Nintendo clearly prioritizes handheld during development, before transferring to the docked version close to launch. Check out the comparison by DigitalFoundry below.
Super Mario Odyssey is currently 900p docked, 720p mobile
Handheld runs at a smooth 60fps.