Can a higher wattage electronic ballast, be safely used to drive a
lower voltage fluorescent lamp - or is there some kind of current
sensing on the output that will cause damage to a lower-wattage lamp?

And secondly - regarding pin connections - I don't have a connection
diagram for the 4-pin circular lamp I want to drive. Is there some
rule of thumb about the output connections to 4-pin fittings - are
there in fact 2 pairs of identical outputs?