Where to install water shutoff valve
I would leave the copper attached to the CPVC, if taint broke don't fix it.
I would cut it down a little so your new valves are not so high, just below the drain pipe.
You can use compression, solder or push to connect valves for 1/2&quot; copper.
I would add support for the pipes,  put a piece of wood horizontal on the wall and use copper pipe standoff's or straps to secure the pipes and keep them from flexing when using the valves.