running aoe4 on a pc . recently upgraded to 16 gig ram and all else seems to be fine. however first mod i downloaded was a “population 300” mod and when testing with the mongols on an extra large map vs the chinese, it limits the mongols to 210, not 300. i thought this must be an easy fix for someone to tell me what to do. the mod does SOMETHING, it raises to 210 from 200.
If building gers and / or town centers doesn’t increase the mongol popcap then it’s probably a bug in that specfic mods data and you may want to keep looking for one that works 
ok. yeh played rus and they get up to 300. will try another. it may have something to do with housing as mongols cannot build them.