[leereeves]

It seems to be a rule that data expands to fill the available bandwidth.

With that in mind, what's the relative transmission power for 4G vs 5G if both are using all their respective maximum bandwidth?

[Arnt]

5G the tiniest bit lower, because the error correction is a tiny bit better, so the receiver can tell the transmitter to adjust the volume a little bit, assuming the same distance/path.

Or the same if you want to compare early 5G with late 4G, because this is really the same thing. They deploy improvements all the time, and after some number of improvements they rename.