Hi Phil You've asked several questions....lets see if I can give a little assistance.
You should plan on running all of your wire and plumbing BEFORE you put down subflooring. Once its down, you won't want to pull it back up.
Yes, a knee-wall will be required if you make the attic into living space. Depending on the pitch of your roof and whether you get snow where you are or not will determine what you put the knee-wall studs on. If you have a 4 or 5 pitch roof and are in a snow zone, then the kneewall framing must go onto something that will carry and distribute weight...as most of the added weight will be carried by this wall that is often 1/3 to 1/2 the way between the bottom of the rafter and the top of the rafter. In snow zones, a shallow pitch roof may deflect downward considerably when snow gets piled on it. I make up a plywood sandwitch beam with 2X material, supporting it only over weight bearing framing and putting the kneewall framing on top of that.
Also, your rafters corresponding right and left pieces, should have a collar tie going between them to keep them together and resist 'spreading'....it also provides a great base for ceiling ceiling drywall.