Wow you are going all out !
It would probably be best to just go with 2-way sli, as far as I'm aware Nvidia is only allowing 2-way sli with games and 3 - 4 way sli for certain benchmarks with pascal.
You won't need a 480 radiator for each gpu, you could use one 480 rad for two gpu's and one for your cpu or you could put two pascal Titans and your cpu all on one 480 radiator. You don't need to go overboard with the radiators unless of course you want to.
🙂Skylake-X you are referring to is Kabylake and should be coming sometime early in 2017, I'm not sure of an exact release date.
You can get custom made gpu backplates here, if you go with these contact them to make sure you get the right one, they can do it in any color and probably the ROG logo too.
http://www.v1tech.com/shop/backplates/titan-x-backplates/For tubing I use the mayhems ultra clear, this is the biggest size available 1/2" x 3/4"
http://www.performance-pcs.com/mayhems-ultra-clear-tubing-1-2-x-3-4-13-19mm-tubing.htmlBe sure your fittings are the same size, I like to show people these.
http://www.performance-pcs.com/fittings-connectors/monsoon-chain-gun-compression-fittings-1-2-x-3-4-...Coolant - Koolance is the only brand that recommends changing every 3 years all other brands recommend changing every year. These are just some suggestions you can go all EK, waterblocks, Rads, fittings, tubing, reservoir, pump, coolant. Red coolant is the color that stains the most because of the amount of dye needed to achieve the proper color, if you're worried about staining you might want to go with another color.
ROG and EK is as good as it gets.
To give you an idea here is my pc with 3/8" x 5/8" tubing, scroll down to the pictures.
https://rog.asus.com/forum/showthread.php?82540-Maximus-VIII-FormulaIf you need help choosing water cooling parts just say so.
