Zelda BotW received a patch that has reportedly improved performance significantly.

https://www.reddit.com/r/Games/comments/62iv1n/the_legend_of_zelda_breath_of_the_wild_receives/

http://www.neogaf.com/forum/showthread.php?t=1356779

It is available on Wii U as well. Someone posted this and this. It doesn't fix all the framerate issues, but there should be some noticeable improvements.

Hopefully this patch helps performance on Cemu too.