Is a bitstring easier to compress if it has lower Kolmogorov complexity?
I think your intuition is not correct. We can't effectively reason over the space of all programs, even all programs up to a given size (e.g. 90 for A and 10 for b) and it's not certain what the units are in your given KC measures for B and A. 

As a simple example, imagine a program B that decompressed a highly compressible message and then encrypted it using some cipher and a hardcoded key. And imagine a different program A that simply output a hardcoded random string of the same length as the one produced in B. Given a long enough output, you could make K(output(B)) &lt;&lt; K(output(A)), but both would be highly uncompressible without having the decryption key for B available.

What you're talking about sounds something like this:  https://en.wikipedia.org/wiki/Algorithmic_probability. It is uncomputable, but if you are willing to e.g. limit the execution time of programs and randomly sample from random programs, you can start to analyze very simple examples.