I bought a Switch the other week (OLED version, but same powered hardware I guess?) and am playing BotW just now. Two things that create some lag I've noticed: the forest area with the master sword, and when blowing up lots of explosive crates.
Breath of the Wild is quite terrible on the Wii U. You get frame stutters when there’s more content on screen than just a few enemies and the resolution + aliasing are really hard on the eyes. Load times as well are longer.
I stopped playing on Wii U and rebought it for the Switch where it’s significantly better.