I just ran a bunch of copper in my garage. I have a 60 gal vert compressor and do mostly car-related stuff. I used 3/4 type L. What I found is most big-box stores around here had L and M, but no K.
The L costs more but type M is really light. It would dent easily, and just seemed kinda light-in-the-a _ _ . Just my opinion.
I pressurized everything to low pressure and leak-checked it before putting full pressure on it. Then I ran it up to full pressure and kept my distance for a few hours. I would recommend restraining the pipe to wall framing or something substantial. Tons of stored energy in compressed air and if a sweat joint lets go it could ruin your day. It has been working like a champ for a month or so now. Looks nice too.
I ended up with maybe $350.00 in pipe, fittings, valves, air chucks and filters. That **** is expensive. Many use black iron, but I could not cut and thread it so went with copper.
