I followed the last major online qualifier on my phone, and frankly, the easiest place to start is by analyzing the most recent head-to-head matches, like the last five maps played between two teams. Team rosters have changed a lot this summer, so anything older than two months seems a bit unreliable to me.

The only thing worth noting is that manually compiling statistics misses the mid-tournament dynamics. Modern esports analysis tools take into account not only historical data but also the teams' current form. For example, predictions that are actually updated as the tournament bracket evolves can be found here ​https://winio.ai/forecasts​​​ The result of a single map can completely change the confidence level, so static spreadsheets quickly become outdated.