The larger the online tournament, the more challenging it is to run. Since teams don’t have to travel to online tournaments, you theoretically could attract teams from across the country (or world). PACE advises against this and encourages teams and TDs to mainly stick to the same circuit as in-person events (although bringing in staffers from outside of your region is definitely encouraged).
The most important limit on tournament size is the number of staffers you have. Ideally you should have 1 staffer for every team at the tournament (meaning about 2 staffers per room).
If your tournament will have more than 20 teams, you’ll most likely want to split up the tournament into separate Discord servers. The reason for this is because Discord servers tend to degrade when many people are connected to them in a video chat. This document doesn’t currently cover this split-server scenario but we hope to add guidance for this in the future.
In general, it’s a good idea to start small with your first tournament. Once you get the hang of it, then consider scaling up for your 2nd or 3rd online tournament.
If hosting on Zoom or Google Meet, note that they often have a limit of 100 people per call.