No, QMC has not stated QE for solar, but efficiency is relative to the context as you say, "I know the story on LCOE & how efficiency numbers don't matter & all that," You also know that BOD member Dr Ghassan Jabbour would head up the R&D and he is ultra-expert on QD and printing QD by R2R. Only he knows how long from concept to first commercial production. I won't guess.

I just quoted that India is paying $740M/GW on the other board. I have said Solterra could do it for 5X less, or app. $150M/GW.

The factors or variables include-
CAPEX - how much to construct and
OPEX - how much to operate

Answer - Compared to Silicon Solar Panel production, Capex and Opex are nothing.

Solar Cell Efficiency -
Cost of Materials -
Speed of Production -
Value of End Product increased by QD -
Regionality concept

Answer -

Solar Cell Efficiency - if the cost of production is 5X lower for the same amount of watts, then the efficiency is only relevant relative to siting, and if siting on a solar farm, it is of no consequence. The cells will not be 5x less efficient.
Cost of Materials - I foresee that each solar factory could have its own dedicated CFP machine so costs of production for QD would be very low.
Speed of Production - The R2R would start at 100meters/minute and increase to a maximum of 600meters/minute. That info is per the R2R makers.
Value of End Product increased by QD - That is Solterra's profit.
Regionality concept - Licensing franchises by region - low risk, repeatable profit.