For tournaments, well I helped referee a school (high school/college) esports league here in Montreal, and helped referee an NHL tournament at DreamHack Montreal 2019
It was not running, like managing the bracket, but mostly working to make the event run as smooth as possible. For the esports league it was wrangling the kids (14-20 yrs old when you are almost 30 are kids) so the game started on time. The NHL tournament was mostly bug solving when controllers didnt sync or people were unsure how things worked