no return springs other than a very strong spring inside the rear pulley.. it forces the rear pully to stay closed.
on my bike, using stock weights on a flat road from a dead stop, the variator almost immediately goes to top gear. I'd estimate RPM to be about 2,500 to 3,000. This RPM would depend on acceleration rate and wind resistance, etc. So, RPM is even lower with a tail wind.
Of course, if i hit a headwind or go up a hill, RPM drops. The variator then shifts to a lower gear. And road speed can remain the unchanged.
Thepoint is that RPM and road speed are practically unrelated. I once mounted a tach for some tuning feedback and it was useless.
The effect of load as an independent force is hard for me to picture..
But i know that increased load causes RPM to drop..
And when RPM drops the weights have less outward force.
The rear pulley/spring is then able to pull the belt and so closes the front pulley.. which lowers the gear ratio.