Is there a significant difference between the 99's and the auto control units on the 00/01's?

I assume that there is, because it appears that the fan controls are integral to the auto control unit on the 00/01s.
That being the case, it's probably still the same blower motor between the two models.
The 00/01s have a power transistor paralleled with the max-high relay, everything else is in the control unit.

Good thing too- it has warmed up to 20 degrees today.
Sunday it was -38.