--MOD AND PLAY--
Download NSMBW ISO, download wiiscrubber 1.4 pc, launch makekeybin.exe type 42 and press generate, then launch wiiscrubber 1.4 pc, open wii partition (hit the + icon), scroll down intill you find stage and then 01-01.arc (unless you modded a different level), right click 01-01.arc and click "replace" and replace it with your modded 01-01.arc. close wii srubber and try launching your modded .iso with dolphin.
Fully deinstall dolphin (also auto generated folder in download-folder/document-folder, download developer dolphin not beta, touch NO SETTINGS except the backend, set to Direct3D 11 (graphics-> Backend-> change to Direct3D 11)
--ERRORS/MODDED LEVELS NOT WORKING (SERIOUSLY READ THIS!!!)--
If you get error, add pad of newersmb and right click the game and click "open wii save folder"
You will get send to a folder called "data"
Go 1 directory back and delete "content" and "data" and other files if there are any.
This will refresh data (modded levels will refresh)
You have to do that EVERY time when you make changes to a level.
To apply modded levels to iso use wiiscubber 1.4 pc.
If there are still any errors try dragging the file into dolphin, not launching it directly from dolphin.
IF YOU NEED HELP WITH SOMETHING TELL ME AND I WILL HELP YOU.
hope i helped