All the performances are documented, we can have all sorts of debates, enlivened by the fact that the fixed prop was good for climb or top speed, but not both, and prop makes varied on the same a/c.

Nobody had air/air radio, the RAF experimented with air/ground, but IIRC it wasn't two-way.

In 1917-18 combats took place over 20,000ft, without O2. Fliers were tough in those days. Some German recce aircraft had oxygen, or at least crew carried a personal bottle, and sucked a tube.