Don’t care about emulation performance, it’s apple and oranges. Lots of games more impressive than Bloodstained have been adapted successfully to the Switch. Compromises exist but they don’t include making them almost unplayable.

Anyway, regarding why Bloodstained specifically should have been easier on Switch than Wii U, it’s not only about the Switch being more powerful or a more modern architecture than a Wii U or a Vita (though it is).

It’s also that the version of unreal engine (4) they were developing the game on wasn’t even officially supported on the Wii U. They made a point in their crowdfunding campaign that they were enlisting the help of Armature, former Retro Studios Devs with experience in porting. They needed them to do the necessary development to adapt a UE4 game to Wii U. Back then Armature were even proposing to release their work once done for other studios wanting to do the same.

Development went longer than expected, Wii U was a big commercial failure and its life was cut short, so I can see why they cancelled that and went to Switch instead. But UE4 is officially and fully supported on Switch, so that barrier didn’t exist anymore.