Personnaly, i hate when some settings are changed on my back while changing another setting, and such a change would need an option to be disabled. For example, i think adding a dropdown option for default setting of popCap with { 100, 300, 500, "depending on number of players" } would be ok.

we already know well when populcation cap is best at which playersize

I don't know :-)

Agree that persisting settings is preferable. (Mostly people play random maps, setup teams and civs, victory condition, then decide to select a different map. Would be bad if those accepted settings would be overwritten then, as they are with scenario or skirmish maps).

But also agree that it's bad if people start a 300 capped game with 8 players, reach 8*300 pop and then get an unplayable game with lag of doom.
8*100 pop was basically the most that the engine could support up to Alpha 18.
Then with Itms new pathfinder in Alpha 19, 8*150 had become the new limit.

Perhaps we could just show a Yes/No message box for the host on attempted gamestart saying that it's too much pop for the engine?
Remember we also have some alpha hints somewhere saying that the game lags with too much pop because it's in such a terrible alpha state ;)

maybe just tooltip for now until any last changes on gamesetup happened to a22, so we have some hint now?

maybe yes/no message box later (step)?

It is true that its not set in stone that it has to lag if exceeding those numbers. It is typically starting to lag when massing a lot of units in a small area (they bump into each other often, then they need new paths again).
For bots, the numbers are similar in my experience. However we should do actual testing, starting games with deathmatch resources and those population figures, comparing them to matches exceeding those population counts.

If we can conclude that this is true on average, I think a yes/no hint when launching the game plus a tooltip would help preventing lag of doom games for people who are not aware that this should be limited.

The same is true for very large mapsizes btw. and mgiht receive an equal treatment.

In D232#12395, @elexis wrote:

It is true that its not set in stone that it has to lag if exceeding those numbers. It is typically starting to lag when massing a lot of units in a small area (they bump into each other often, then they need new paths again).
For bots, the numbers are similar in my experience. However we should do actual testing, starting games with deathmatch resources and those population figures, comparing them to matches exceeding those population counts.

If we can conclude that this is true on average, I think a yes/no hint when launching the game plus a tooltip would help preventing lag of doom games for people who are not aware that this should be limited.

The same is true for very large mapsizes btw. and mgiht receive an equal treatment.

y and if dont get confident numbers we can say as tooltip it might/can lag due to high population and/or mapsize.. ive seen we already have a tooltip at mapsize onmouseover put not at poplimit, maybe should, say ther it also depends on popcap but maybe having some numbers to advice is allover the best.xD