This is correct. I had some cats who self-regulate and some who will overeat. The overeater was a stray cat initially which explains the behaviour.

This is very true.

I have two cats, male and female. They are from the same litter, and have had the same upbringing. One is quite chubby, the other stays fairly thin. The chubby one is also naturally lazier.

Different cats have different histories with food security too, which probably plays a role.