The difference, to answer your question, is the physics of the games because a PAL output (Europe) has more lines to display than NTSC outputs (USA/Japan). This means that PAL versions are generally not accepted for speedruns. To give you a concrete example, in Super Metroid, Samus does not jump in the same way depending on the version.

What is the difference? I'm interested. I just know that the line-up on Super Famicom Classic is different from the US/EUR versions