Replacing copper pipe for water line M or L? fittings do they come M or L? type of gas for sweating?propane?

I've always chosen type L it is a heavier wall thickness- much more resistant to abuse & corrosion. the fittings all seem to be "L" or even "k" an even heavier wall thickness. propane would be fine- ample heat, relatively cheap. If you are going to do alot of this you may consider a prest-o-lite torch which uses air and acetylene.