It's pretty much impossible to gauge someone's personality without interacting with them on a regular basis. I have never been a college student athlete, let along one that requires ND's standards and I don't know what it entails as far as workload goes although I imagine it can be pretty difficult.
When it comes to football, I actually prefer the calm, cool and collected type of QB who at the same time, isn't afraid to display emotion at times because sometimes being overly emotional can lead to poor decisions.
I believe either Kizer or Zaire is fully capable of leading ND football. They're obviously 1A and 1B(Take your pick) but it will probably come down to the type of offense BK wants to run and I don't think anyone really knows that for certain. ND has better offensive depth than they have had in awhile so it could go in either direction. Since the WR corp is fairly inexperienced, I lean towards believing it will be run heavy, which would probably favor Zaire. Another aspect that makes it hard to figure out is that BK's offense has been more run heavy one year, more pass happy in another based on personnel.
Either way, we'll find out fairly soon. Personally, I prefer a run heavy, ball control scheme but I don't really care as long as ND is winning.