These are privacy respecting tools to consider. But what signifies as a big file? Any file that you cannot seem to send through an encrypted messaging app like Signal or Telegram’s secret chat. Ideally, it should be anything more than 1 GB.
Internxt is probably the most convenient being online, whilst an option like OninionShare is fully peer-to-peer but then does require the app to be installed at both ends (but is available for all generally used platforms).