The Zelda framerate drops are a result of it being a ported Wii U game. 720p is native for BotW, and Wii U gets lots of drops at 720p anyway. OTOH it runs flawlessly in Switch portable mode. What this shows us is that Switch is more powerful than Wii U, even in portable mode, and that's about 40% of what it can do in docked mode.
THIS for fuck's sake. People are having serious trouble understand why the Switch, supposedly more powerful than a Wii U, has framerate drops. The game isn't made for the Switch, that is all. And Breath of the Wild is DEFINITIVELY not a technical proof of what the Switch is capable of. I am pretty sure that within the year, we'll see far more impressive games than this one.