I strongly advise against using the spreadsheet instead of the editor. The spreadsheet is clunky, it has more bugs and it would be harder for me to provide support in case of any errors since it has an older code written in VBA. The only advantages being file size and working on Windows 98. If you still want to use it, let me know.
It was actually created for a cc-only league my friend Emerson used to run. The option of changing setups is not really great because ccs are always at their faster with rear wings set to 1, with front wings being of minor effect in lap times. So there would be only gears as settings for us to play. Much more interesting IMO, is the ability to assign pitstop strategies if the races you are going to make allow for them. Both the spreadsheet and the editor allow it.
Going back to changing setups, if you use the editor (or the spreadsheet) to make them all equal, you make sure your GP2Edit grips are more relevant in the races since GP2 randomises the wings and having higher rear wings means the cc will be slower (for instance, if the track .dat setup is wings 12/10 - gears 33 40 48 53 58 63, some ccs will end up with wings 12/9 and others with 12/11).
And here goes my car bitmap