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.

Having a powered sub is a better way to control the sound - the bass will be tighter and louder, less “boomy” but the trade off is you have to power it separately and deal with The sub enclosure being outside the game, which not everybody likes.