Madame President the Vice President here. In honor of the New Dragonball Z movie that just came out and is currently in theaters this week only. I'm going to talk about how the older movies work.
Dragonball Z and the battle of the gods.
Each movie is set up to fill the important parts of an arc with no filler into an hour and a half.
An evil either shows up or is going to show up, the Z-fighters gather together to stop said evil, lose the first battle, Eventually something happens for them to work together or someone uses extra power and they win the second fight.
Every movie can be placed in the timeline, this is also true for Dragonball GT's one OVA.
The placement in the timeline is not perfect but a window, this let's us know who knows what powers and what skills exist. So you don't have to ask why don't they just do this or that to win. Two Villains people really liked, these were Cooler(Freezia's brother) and Broly(the baby in the crib next to Goku when they were born), Broly were so popular that after the first Brolly movie they made another,
Then a different Villain, Then a third Broly Movie. After that we made the second Cooler movie.
Tomorrow I'm going to see the Battle of the Gods So I'll do a post about it.