"Confused ...sure wont be the last time with this build .."
That would be an understatement.
Once you get the basic frame assembled, you are pretty much on your own.
I built a hex and I am about 6-months in front of you, and still trying to figure out the details.
I run my cables through the arms and mount the ESC's, well, in various places. As I add stuff, I need to make room for the new parts, usually by moving an ESC. Use Velcro until you are really finished placement of the ESCs.
Note the white tabs under the radios. This is the 3M Command adhesive strips. This way I can pull the tab to remove the strips and relocate the radios as needed.
Note the balls on the landing gear. You will crash. You will break the landing gear. You will likely bend an arm. You most assuredly will break props. Buy spare parts now.
The landing gear is nice for good landings, but those are remarkably rare. You will either drop in from a few feet, or be moving laterally. If you're over grass, you are likely to snag the 3DR gear on the grass and flip. Turning a hard landing into a prop replacement. If you feel confident wth your landings later, just slip the balls off.
The balls are Easton 9-inch practice balls. Ordinary Wiffle balls won't work. The Easton balls are a soft, flexible plastic and the others are a hard plastic. Just cut a gap between two holes and the 3DR landing gear just slips inside.
But, I gave up on the stock landing gear. I fabricated my own more forgiving gear with a 1/2-inch pipe insulation and the Easton balls. These are virtually indestructible. One change since this photo is two more Ty-wraps closer to the crook of the "T". This adds stability. In my case this is temporary while I continue to learn to fly. When I add a camera gimbal I will need new landing gear to raise the whole craft a few inches.
Here's a photo with another idea for running the wires. These are on the outside and considerably shorter.
Oh - if you use the balls, paint the outboard balls black. My "Forward" ball is left fluorescent yellow. This aids greatly in visually orienting your copter position. As long as the yellow is between the blacks, I know that the copter is aligned with me.