I can’t mod my Wii U, what is the fastest way to get 99 of all power ups
Without modding?

Personally I never bothered to download the save with 99 of everything either, so what I did was go to a mushroom house and get around 20 of each powerup. You don't actually need 99 of everything, but you can do the same to get 99 if you feel like you need that many. I also used a mushroom house cheat sheet that you can find somewhere online to make it easier to get items quickly

Yeah it’s op

It doesn't take that long, I maxed out a profile by spamming World 7 mushroom house with an online map, while watching yt most of the time. Not sure if that is the most efficient way, but it worked well for me.