To provide you with more freedom, you can create tournaments according to your own criteria. On the left panel of the interface, in the “Tournaments” tab, there’s a button named “Create a tournament” which pops up a panel as shown in the below image.
In the first drop-down menu you define the type of tournament. A Swiss system will offer pairing between players with the same number of points. whereas a round-robin tournament will make all players play against all others. A "double" round-robin tournament will in fact be a double round-robin tournament where each player will meet all the others, once with the white pieces and once with the black pieces.
You can also set an Elo range for participants. The game speed, with or without increments, for example 5 + 2 will give 5-minute games for each player with an addition of 2 seconds for each move. And finally, you can choose the order of the tiebreak system.
Moreover, you can create private tournaments restricted to a list of usernames that you define, or public tournaments open to all players. Feel free to add a blurb that is visible to all in the tournament profile.