Understand, I'm not, nor ever have been pro. Not even a very serious hobbyist.
But, when I was out and about, I'd keep two in my bag.
One was a more automatic job with higher speed film (say 800+) for shots that I couldn't set up because they were unexpected, and my oldest manual camera for dialing in exact shots that was loaded with a slower iso film, maybe 200 or lower. Fuji was what I usually went for.
I was usually either taking landscapes or other relatively static nature pics, or pics of animals (pets, livestock, or wild), so I never managed to be fully happy with all the pictures on a roll if I didn't have two set up.
If I could only carry one, it would be the autofocus one, but loaded with a 400 ish fuji or Kodak (pretty much the only two brands I could guarantee finding without ordering stuff).
But I was not a regular b&w user, and it's my understanding that those films don't perform exactly the same at a given iso in every lighting condition.
But, yeah, two cameras was my default if I was going out specifically to take pictures.