Hi
The installation guide on youtube is for any win95 games. The mgc file for fallout has valid expert settings for running win95, dont search for fallout 2 specific settings. Only fallout specific settings are on screen buttons. So just duplicate fallout2 profile, delete all buttons and add own.
2GB file included on youtube is not fallout specific, place there which game you want. You can rename it to something else, but fix its name in expert settings.
Just imagine that 3rd part of video guide is not about fallout, but for something else. Main point is that dosbox controls win95 not fallout