Talk to your electrician. He can place the sub-panel, you could probably handle the rest from there. Don’t attempt to saddle him with a bunch of unusual requirements that you really have no knowledge of. Tell him you want quality materials, panel with copper buss work, copper wire. Give him the basic idea of what you’re trying to do, and why. If he’s onboard, let him do his job. That’s my advice, anyway. I’ve worked in residential construction for 32 years. Good luck.
The wire won’t be a single, but individual insulated #4 wires, THHN or THWN, I believe, in PVC conduit from panel to panel, and might also include a bare ground. Not sure about that last bit, I can’t remember the code requirements for sub-panels. I’m not an electrician.
I just reread your post about the ongoing new construction. Of course, I don't know where you are, but here, our electrical inspector would more than frown on you doing any electrical work while your electrician is doing the job under his permit. Ask him.
The wire won’t be a single, but individual insulated #4 wires, THHN or THWN, I believe, in PVC conduit from panel to panel, and might also include a bare ground. Not sure about that last bit, I can’t remember the code requirements for sub-panels. I’m not an electrician.
I just reread your post about the ongoing new construction. Of course, I don't know where you are, but here, our electrical inspector would more than frown on you doing any electrical work while your electrician is doing the job under his permit. Ask him.