Breaking Closed Guard is a good starting point for a BJJ practitioner. Mainly because a large number of beginner rolls get bogged down in Closed Guard. It can be hard for a white belt to attack from bottom and easy for the person on top to stall. You will live and die stuck here if you don't know how to break free. This is a waste of precious mat time.
For this first portion, your goal will simply be to break the opponent's legs open, nothing more. Depending on your body type and the body type of your opponent, some techniques might work better than others, but the ones shown here have the highest success rates.
Also, know that there are a lot of really bad Closed Guard breaks being taught out there. Part of this is because some of the more traditional Closed Guard are still taught at some academies. Also, Closed Guard breaking does not have a huge focus in modern competitive BJJ for various reasons so it's not always given proper attention at big academies.