I'd get a 60-75 gallon tank with a 5 hp twin cylinder compressor.
That will supply you with enough air for almost anything you want to do.
For an impact I would buy the most powerful 1/2" drive I could afford and a set of long, short and swivel impact sockets.
That's basically what I did 20+ years ago and I have never needed more of either for any build or project I have done. It pays to get the good stuff the first time if you can.