There are three online and one offline play modes.

Online Play Modes

Online play can be in any configuration, two people sitting on a couch teamed up with two other people online, four players local playing another team of four online, or everyone remote.. etc. The only rule is that everyone who shares a screen (ie.. sitting next to each other) has to be on the same team.

Quick Play

Hop in solo or with your friends and play against other teams in exhibition matches that don't effect your overall score.

Quick Play places you into a match as quickly as possible. This means you will likely be dropped into the middle of an already started match when you first enter Quick Play. Additionally, Quick Play will use bots to fill in for absent team mates. Neither of these conditions will ever happen in Ranked Mode. Quick Play naturally has no effect on your ranking.

Ranked

Put it all on the line. Hop in solo and get matched with players of your skill level, or join in with three friends and compete against other online teams to increase your score, rise in the leaderboards, or face the Black Team!

Custom Match

Create a private game and invite up to eight players online to battle for bragging rights!

Local Play Mode

Local Wireless

Local Wireless allows two Nintendo Switch consoles to connect, for a total of eight players on two screens.

Step by Step Instructions for Offline Play with Nintendo Switch

1. In the Main Screen press L+R to add up to 4 Controllers (from the players who wanna play)
2. Then every player has to press -/+ to join
3. Go to Local Wireless and create a room. (If you have a second Switch for 8 players do the same but don‘t create a room just join the one that should be there (didn‘t test with secound switch yet)
4. Now every player can decide what role they want to play
5. In match settings you can choose which maps can be played
6. Now just start the game and have fun!

source official trello board

additional source @Sevatoxin#8616 on Discord