These are the "same thing" -- energy per bit / noise density chooses your bit error rate (and not enough energy per bit goes off a cliff to 50% errors where you don't transfer any information).
More power increases throughput for a given bandwidth (not proportionally), but we're talking about 20kW, which is not so much (the path loss is high).
It increases the channel capacity. Bandwidth (spectral occupancy) remains the same. (Apart from increased distortion associated with higher-power transmitters in the real world, of course.)
