If you're going to compare Snake Pass to a launch title, comparing them to exclusives that didn't need to account for features that exist or are missing on other platforms isn't the right way to go about it. It'd be more like Battlefield 4, Fifa 14 or COD: Ghosts. All of which ran on hardware that was significantly less powerful than the PS4/XBO. Also the difference in power and capabilities between PS4/XBO and PS3/X360 is far greater than the difference between PS4/XBO and the Nintendo Switch.
There's no reason Tekken 7 wouldn't run on the Switch.
Looking at the PC port of the game, it scales down quite far in its requirements. It obviously won't be a graphical match for PS4/XBO, but it also wouldn't necessarily require a "massive" downgrade. It may or it may not.
Regards,
SB