All Tesla battery packs have 96 “rows” of cells where all the cells in a row are connected in parallel with the rows connected in series. Each row of cells is charged at 4.2 volts. 96 rows therefore are charged at 403.2 volts (96x4.2). The only variable available is the charging current per cell as all cells in a pack are charged at the same current. The 18650 cells were limited by Tesla to a maximum of 4 amps per cell. This was for two reasons: To limit the heat generated in the cells by the charging current and to limit cell degradation. I’ll spare you the details. The 85/90 pack has 74 cells per row. 74x 4 x 96 x 4.2 ~ 120 kw, the limit on power for V1 Superchargers.
The 2170 cells were initially limited to 6 amps per cell because the larger cell cross-section gave the cells 2/3 the resistance of the 18650s for the same amount of heat despite the higher current. But I believe that the Model 3 LR battery pack has a more capable cooling system than the 85/90 packs. Possibly also true of the 100 pack.
This enables them to raise the peak charging current per cell for the 2170 packs for maybe 15 minutes per before tapering off. The maximum power that can be applied was therefore increased in proportion to the higher current, maybe 150 kw. It may be that the 100 pack has a cooling system that can also be tweaked. If so, that pack with a software update may tolerate higher max charging current/power, shortening charging time for that pack.
If you think of an 85/90 pack as 7104 resistors of .015 ohms dissipating 4 amps each, the total peak power dissipated is 16 x .015 x 7104 = 1700 watts or the equivalent of about 17 100 watt light bulbs, a lot of heat to get rid of.