As far as I remember QR's opup system is entirely unsophisticated.

First-up will of course be staff travellers with firm bookings in a lower cabin but priority for accommodation in a higher cabin.

Then it will be determined on an ad-hoc basis by the ops control centre and airport managers. I do not think that there are any set tools or processes in place but I do know that they try and accommodate high status passengers first.

To be honest, QR's overbooking processes are (or at least were to recently) pretty good and opup/opdown requirements are low compared with industry standards.

Contrary to popular opinion I don't think that nationality counts for much in these decisions.