While Decaf doesn’t emulate the Wii U as good as CEMU at the moment, it is an extremely promising start and is already making big strides to catch up to CEMU in emulation capabilities.
Initially Decaf emulator was a Windows 10 only Wii U emulator, this was due to its initial use of DirectX 12. However the primary developer of Decaf, Exjam, made the decision to drop DirectX 12 in favour of OpenGL 4.5. This allows Decaf emulator to actually be multi-platform.
Decaf is already able to run some commercial Wii U games. However at this moment you are likely to run into an assortment of graphical issues and severe bugs at this moment. Decaf is very much in the experimental stage, but Decaf has made quick progress in just a few short months.