[Stout72]

67cst, 12.3 cfm will probably be plenty, but you have to look at what output pressure that flow rate corresponds to. Most air powered tools operate at 90 psi. Check the specs for the specific tools you're using, decide how many tools will be operating at once, then size your compressor accordingly.

As for plumbing, use whatever you're comfortable with installing. I'd stay away from plastic for compressed air. Threaded galv pipe would be best, most durable. Rigid copper is cool, but you'd have a lot of fittings to solder. Since the compressor max pressure is probably 150 psi, I bet you could use copper tubing and compression fittings. Use a flex connection between the compressor outlet and your garage plumbing to absorb the vibration from the compressor. Aeroquip hose and fittings are good for this. For multiple outlets, tee off a main line run from one end of your garage to the other, you can have as many as you want. Install quick-disconnects at each tee.

Use a filter/dryer between the outlet of the compressor and your main line plumbing to keep everything dry.

For your air tools, be sure to use an inline oiler and a dedicated hose. Install a quick-disconnect male fitting on the inlet of the oiler so you can plug it in to any of the taps you install.