Interesting post with a lot of points. It's been many years since I fooled with those one-tube CW transmitters it seemed everyone used to build in the older days. I remember the degree of chirp was more related to the integrity of the power supply. The more regulated the supply, the less the chirp. In the case of a not-so-stable power supply, it helped chirp to drop the plate voltage on the tube a bit to reduce the sudden pull on the supply when the key connected. The RF output would of course drop, but if you were shooting for true QRP you might not be able to run full plate voltage on tubes like the 6AQ5 anyway.