How densely populated was the kingdom of Macedon compared to other hellenic ethnicities/states at the time?. It seems from what I've read and listened to like diadochi manpower was dependant on Macedonians even for the rank and file troops. Was it just a byproduct of Philip and Alexander building up the army or were they actually a larger ethnic group as well?
Side note how is diadochi supposed to be pronounced? I feel like I've heard it 3 different ways and I'm afraid to say it now lol.
The Greek spelling of the word is διάδοχοι. It is the masculine plural nominative of διάδοχος, which is itself the noun derived from the verb διαδέχομαι, "receive one from another; succeed, replace". If you note the accent on the word διάδοχοι, you see the stress is technically on the antepenultimate syllable (third from the back), so properly "dee-AH-do-khoi", not "DEE-uh-DOH-khoi" or "dia-doh-KHOI."
For the population question: the short answer is that Macedonia had a lot of manpower, especially in the 5th and 4th centuries, but we do not have very many reliable statistics or comparative data. There is a related question here . Philip II had greatly increased the manpower of the military by altering traditional modes of recruitment and even statuses. See here for a quick mention of that.