Ok, so I can’t do the first USB method as I’m in Windows (So, as you said, there’s only the 56MB partition available)
i’m not sure i understand this. you don’t need to see the SD card file structure on windows if you’re doing the USB method – (reiterating the video) you put the USB in the pi whilst retropie is running, and it will create a folder structure. connect the USB to your pc then put the roms in the relevant directories on the USB, and then you put it in the pi and it will transfer everything to your SD card. you never need to access the SD card on your PC.