For whatever reason, Firefox uses 30-40% CPU at all times on my 2020 Intel Macbook, meaning battery life is quite short and the slightest bit of load on top will trigger the fan, which hardly ever happens when using Brave or Chrome instead. FF worked well enough for a year or so once they got acceleration to work properly on macOS, then this happened. Besides, I need to run Chrome anyway for various webapps I need to use that are broken in FF.
For a time outlook 365 wouldn’t receive all keystrokes, this was for months, when I finally got fed up I googled it and users reporting it resolved their issue by using chrome.