Hi,
I can't assist with the diff of multi vs normal... but...
I used almost 7 9l bags on my 220 of 6x3. I did NOT have a very deep substrate.
I would think 6-8 bags would do you fine. Really depends on how deep you plan on...
Also, I had LOTS of hardscape that took up substrate area so you may use more in a bare bottom tank.
Hope this helps.