If you need more than one tier, the most used pedals should be closest to your feet. That's really the only thing I follow.
Then you would need space for the switcher though.I've never used a switching system, but that would allow you to just place them where they fit and control them from the switcher.
True, you'd have to make that choice before the board.Then you would need space for the switcher though.
how many do you want to use?10" deep and 12 feet wide?