I agree on "old friends" for the 2N3904 and 2N2222. However, I can't resist to add that these are, unlike the 2N7000, not MOSFETS but NPN BJTs (bipolar junction transistors). With the point being that BJTs need some amount of control current at the base in contrast to the virtually zero current at the gate of a MOSFET. Judging from the linked pictures, you have compensated for that by using a bigger capacitor to get to the desired turn on time.
In any case, thanks a lot for sharing this journey.

Regards,
Michael