Optiontown allows SK an additional revenue stream where a flight is oversold in a certain lower cabin class. The customer pays to be at the front of the op-up queue. Upgrades with miles are an additional revenue stream where a flight is undersold in a certain higher cabin class.

The only overlap would be in the case of oversold lower cabin class, undersold premium classes. In this case I would assume Optiontown to take preference as the revenue generated to SK is clearly significantly higher. I doubt there will be much risk that one pays double for the same upgrade. These op-ups are manually handled by revenue management and they would have a certain order of priority.

(Of course this is from my armchair CEO position. Who knows what SK would do)