Human information throughput is allegedly only about 10-50 bits per second. This implies an interesting upper bound, in that the information throughput of biological humanity as a whole can't be higher than around 50 * 10^10 = 500Gbit/s. I.e., if all distinguishable actions made by humans were perfectly independent, biological humanity as a whole only has 500Gbit/s of "steering power".

I need to think more about the idea of "steering power" (e.g. some obvious rough edges around amplifying your steering power using external information processing / decision systems), but I have some intuition that one might actually be able to come up with a not-totally-useless concept that lets us say something like "humanity can't stay in 'meaningful control' if we have an unaligned artificial agent with more steering power than humanity, expressed in bits/s".