It looks like going further back helps more than hinders. The backtest tries everything from 50 to 500 games and most competitions I've tested with seem to do best considering around 400 games. I believe there are 380 games in a season of the Premier League so it looks like a full year worth of history would be a sensible default.

No database required. For the pandas error, you can use your package manager (synaptic probably) to install "python3-pandas".

Or try pip3 install pandas from the command line.

You'll likely need to install python3-bs4, python3-selenium and python3-numpy as well.

If you have any other issues, let me know which distro you're using and I'll help as best as I can.

Steven