Easy way to check whether heart races.
2 or 3 beats per second, then it is too high.
For me, that reminds- time to take my Beta Blocker.
How many in one day is normal, I guess there is no standard answer, if you exercise or sleep whole day, the result shall be very different. Isn't it?
I think there are no simple numerical answers to your very broad questions.
I am under the belief that zero or a few not noticed is the "most normal", now for the too many, if we're talking about PVCs and/or PACs many people have thousands (my recollection) a day and just live with it, perhaps they take some beta blocker mediation to reduce the intensity and/or frequency.
It is always best to get a check up with a doctor every year or two (depending on age), even it you don't have palpatations.