As far as cutting copper with a torch, it can't be done. A bandsaw or shear will produce a good cut.
Copper is a great thermal conductor.
This makes it hard to weld with low-energy input processes. Oxyfuel would take a long time to get the weld area hot enough because the metal is quickly pulling the heat away. It can be done, but it takes time to get it hot enough. Oxyfuel is not a preferred method for welding because it does not adequately protect the molten metal. Flux needs to be used.