The first time you run a Wii U ROM, the game will stutter frequently as Cemu builds a "shader cache." Solution: Download a community pre-built transferable shader cache (a .bin file) and place it in cemu\shaderCache\transferable.
This is the critical section. The legality of ROMs is complex. While downloading a copyrighted game you do not own is technically illegal in most jurisdictions (under the DMCA in the US and similar laws abroad), there is a legal pathway: Dumping your own discs. wii u rom
Sites dedicated to Nintendo (like "NX Brew" or similar) offer curated, error-checked ROMs. Private trackers require invites but offer faster download speeds and verified files. The first time you run a Wii U