RTOW for us means only the performance limited take off weight to be honest. Landing weight and fuel is considered during briefing with the preliminary info on the OFP. If any calculations are needed they are done on the back of the flight plan using the good ol' parker pen, indeed the fastest way to do it, usual decision time is less than half a minute. We are rarely if ever limited by landing weight/fuel burn, even if tankering. Fuel is then ordered online and loadcontrol already gets all the infos so the loadsheet could be available once we arrive at the aircraft. The same is true later during the day for subsequent sectors, however ACARS is used instead of the internet currently, internet in the near future.
That way it is possible to get the final loadsheet for the second flight before landing the first one, if flying to a destination where the weather is stable enough to do a performance limited take off weight with the weather data available at that time.