Basic Tube Tech Questions

[SteveH]

All,
So I have had these questions around for a while rummaging through my head.....Can you help me out ?
#1 - How do you determine if a tube would be a good driver tube or not ? If I plot the load line for both a driver tube and my power tube, as long as the voltage swing looks ok, and the driver tube dissipates enough power to drive the power tube - would it work ? Secondly, how DO I calculate what power is needed to drive my tube ? Is it the wattage figure where my load line meets 0v ?
#2 - PSU design. I have no issues calculating PSU draw for SE designs, but what about PP ? I know this has something to do with class A/AB/B, etc - but I am not sure what....

Thanks !