Thanks to user Lethal Legume for helping out.
The Europe 1914 historical map is the only map that has variable population. This post contains a population chart depicted here and some effects of population on important game aspects:
Population effects a lot of game aspects, but that is only noticeable and relevant in this map.
- economic output (resources and output) is proportional to population (2000000 population will have half the output of the default 4000000 pop province)
- corruption naturally is proportional to population
- number of starting infantry is 1 for every 400k population rounded upwards. (highly populated provinces have more starting infantry)
- infantry recruitment time is inversely proportional to population
- upkeepcost of provinces is proportional to population
Double resource provinces in the regular EU map, that are depicted as single resource provinces in this historical map also have double economical output and infantry recruitment. This is because the output is doubled as in regular maps, but below a certain threshold output of 6000, due to population. This implies that you can have very valuable provinces that produce just under 6000 due to population being depicted as single resource provinces.
output = morale/100 * corruption * population/4000000 * constant * bonus_single/double
Money and resource output have a different constant. The bonus factor is either 1 (if the province is a single resource province on the regular map) or 2 (if the province is a double resource province in the regular EU map).
There are 3 pre-game fixed teams in this map. People are unable to attack team-members and to alter team affiliation.
The USA-MEXICO map has the peculiarity that economical output is somewhat variable despite population being homogeneous. Also the maps starts with corruption at 12%.