Hello Peng, thank you for playing
>supply cap for each coven
It says both on the Summoning Circle and on the Control Cage when you select them. (Below the "portrait.") You can also hit Ctrl+Space (or F3) to get an overview of all controlled Coven including their current supply/cap.
>It's a minor thing but you mentioned something about collision so I'll show it in case it's a new bug
Ye thanks for noting it down, something is not quite right.
>It might be more interesting if you had some forced unit variety
Ye interesting point. It used to be that the King sitting on a Coven would lead to both units spawning rather than the same unit twice. It was a bit scuffed as some Coven have alt units you really don’t want too many of, i.e. spellcasters / support units. (Also new players got confused as the buttons to switch unit production did "nothing.")
But probably it is worth bringing this back now that the King has become more mobile so you can just walk around and fight with it while you don’t want the alt spawn.
>they use different upgrade buildings from what I can see
There is always one specific to each and then one building that improves both. Maybe I can yet find a good way to explain it.