Open Dolphin, go to Config > Paths , and add the folder containing your portable WBFS file.

WBFS files strip out the "garbage data" dummy padding used on official physical discs. While a standard Wii disc image (ISO) is always 4.37 GB, a Newer Super Mario Bros. Wii WBFS file is heavily compressed, often taking up less than 1.5 GB.

Running a WBFS file on an actual console provides the most authentic multiplayer experience with original Wiimotes.

If you're searching for the version, you're likely looking for efficiency.