A little of column A, a little of column B. The lower number of talents means less chances for there to be incompatible personalities in the first place, and in the event that there are, they have a far greater talent:manager ratio. Holos start with a shared manager with each new generation and usually get their own after a few months, whereas Nijis are stuck with a manager who's trying to juggle at least 5 other talents forever unless they end up in the very top level in terms of viewers and revenue. More managers juggling fewer talents means they can more quickly and effectively resolve disputes and, if necessary, isolate talents from each other. Hololive/stars managers also handle more of the side tasks such as organiziing events and promoting streams. By comparison, Nijisanji talents are practically indie, handling far more of their workload on their own, making the job more stressful, leading to irritable talents who are more likely to get into fights and their managers are unwilling or unable to mitigate the issues. On the EN side this is particularly bad, with the managers being particularly incompetent/absent. Additionally the EN side has a much lower barrier to entry due to no VTA, so every new hire has far less vetting. Meanwhile Hololive/stars EN appears to be run much more like its JP counterpart than over in Nijisanji. There are certainly some issues going on in the background, and a quick skim of /vt/ will provide many people's speculations thereof, but their leashes are pretty short and you rarely hear about it directly.
