I think it is helpful to orient the perspective of building the legacy Vans aircraft in that you are building the primary structure. The rest of the electrical, avionics, engines, etc are all customizable and the main construction plan does not address these issues. You need to refer to the OP drawings to get ideas of what to be expected. It is also helpful if you can visit other builders in the area, and peruse different build logs. Since you have a lot of experience flying different GA aircraft, you are ahead of the game in term of knowing what you want in your avionics, lightings, etc.
For the wing wiring, I just use snap fittings at the bottom ribs. Running wire, even when the wings are closed, is really easy. I use a long rod to fish the wire but you can get the professional fishing tap reel from Home Depot.
I installed the roll servo, and the Dynon pitot tube before closing the wing. However, there is nothing difficult about installing them after the wings are closed. Slightly less space to work around but they are mounted directly next to the wing access holes. I had to reinstalled my roll servo due to not-so-perfect wiring connector. I am waiting to install all wingtip nav lighting at the end of the build. Again, fishing wires is easy, it is a straight line from root rib to the tip rib. In general the wings accessories are simple. Wait until you start building the fuselage and the non-documented accessories will add up fast.