Hi!

I recently started speedrunning NSMBWii and I'm wondering if there are any modpacks that can help with training (e.g save states or timer) to install on the WII

This should have everything you need to download Saria's practice rom https://sites.google.com/view/nsmb-practice-roms/nsmbw

Also, although it is banned for official runs, you can practice on emulator, too. On emulator, you have access to savestates, which can make practicing much more efficient.