The older RWD models actually hold a LOT more from personal experience. I don't know the exact balls ratio but on our road trips we were able to hold one of the huge cases of water bottles from Walmart in that spot that goes up under the dash with room left over. I was sad when I saw just how much space in the frunk we gave up whenever we went to the AWD versions. Even less room w/the AWD HEPA versions. I'm still not giving either of those features up for more frunk room though.
Several years ago, when we moved twice in 6 months while our new house was being built (first into a much smaller temporary townhouse and then into our new home), we had to put a lot of our belongings into storage for a few months.
Our 2012 S P85 (RWD) was used to move a lot of our stuff - and with the rear seats down - it was amazing how much we could move in one trip, including using the larger (than current) frunk and the underneath storage in the rear.
We only needed to use a larger vehicle for a few items that wouldn't fit in the S.
Our 2017 S 100D still holds a lot - but the frunk is smaller, so we would lose a little of the cargo capacity in that space.
I transported the cabinetry for a small kitchen rehab in two trips. The Home Depot guy was amazed at what fit in there. Later went back and got the full sized stove in. Just couldn’t close the hatch all the way however didn’t have to worry about exhaust fumes wafting back into the cabin. An S easily rivals my old e class Merc wagon or my current midsize Range Rover Velar SUV in hauling capacity