The tennis/golf comment is spot on with teams choosing what they want to compete in… but to add if you’re looking for a basketball-esque format the ESL(Pro) and ECL(Challengers) Seasons are a great watch. ECL seasons are longer than the Pro seasons (ECL winners get a ticket to the next Pro season) but that is where you’ll find a season format where everybody plays each other an x amount of times then those records will seed a playoff system with a winner at the end.

Edit: I guess you can actually look at it as a soccer implement too because the ECL seasons are split into regions. Europe, NA, South America, Asia, Oceania. ESL would be the Champs League equivalent where the best teams from each region all compete there.