A tour pro would have around a dozen Golf balls in there bag per round, just in case. But it is completely up to the player.
== == You can carry as many golf balls as you want.
You would find that a tour pro would use between 12 and 20 golf balls for a four round tournament.
Generally, they do not carry golf balls in their pockets.
Then you go out and buy more.
What clubs are suggested to carry in a golf bag
You can change golf balls in a tournament. As long it is on different holes or the ball is unfit for play, (like if it hit the cart path and was scratched.) But if it was unfit for play you must tell your opponent.
You can carry as many as you like. It doesn't matter as they count on strokes not balls. However, you are expected to use the same ball from tee to the hole unless you loose it, or it becomes unplayable due to damage. You can play a new ball on every hole if you wish.
You could carry 14 if you wanted, but the maximum you would ever need would be four.
In Golf there is no limit to the number of balls used. Depending on difficulty of the course and a players experience one single golfer could use as many balls as they have in their bag at the start of play.
A disc golf bag is designed to carry discs around. Sports such as Frisbee and discus throwing. A regular golf bag is designed to carry golf balls and clubs around.