does anyone else suspect it is important to keep population constantly growing with a standard farmer start up in order to raise maximal tax revenues?

Nope. You might save 5 turns with a really optimized startup, but 5 turns is something I couldn't care less about, you already get 6 extra turns a day from logging in once a day. If you grabbed 100a extra on a well-chosen or well-timed attack, it would more than recover that 5 turns.

Basically, after playing so many years, I just go auto-pilot nowadays, build on "feeling" what is best, and no longer try to optimize the first 300 turns. It's only a few turns, it is way more important to avoid getting retalled during the remainder of the reset.