The volume control is really important to getting the sound right. Don’t skimp on that! You can add the L-Pad later if you want; it’s not too difficult, but IMO nicer to just buy the FF one. They are expensive but really worth it, especially for games like this where the music is critical
Either the 8” or the 10” speaker will be great; if you are concerned I would spring for the 10, but the volume control is more important if you are trying to save a couple bucks.