Hello! I'm excited to hear that you want to play SMB2!

The deal with emulators is this: you are allowed to play on an emulator and submit your Story Mode speedruns to the main leaderboards as long as your finish time is 35 minutes or slower. Once you reach a point where you're strong enough to get below a 35-minute time, you have two options.

The first of these options is to invest in a GameCube/Wii, a copy of the disc, and a capture card. Beyond the sub-35 barrier, it is required to play on hardware in order to submit your runs to the main boards.

However, if this is not a feasible option for you, then you can also submit to the side/miscellaneous leaderboard, titled Story Mode All Levels (Emulator/ISO Loader). This leaderboard is there such that people in your position still have somewhere that they can compete and submit runs without possessing the physical hardware required to play on the main boards.

I hope this helps to clears things up, and I hope you enjoy your time with SMB2! If you ever need any direct help, feel free to reach out to me via Discord at glock in my toyota #6273. Have fun!