Place the T line on the pumps inlet,That allows for easier filling and bleeding.
As far as order of components the "Best" set up is one where you have the least tubing and the least amount of bends,avoid the hype of rad placment,It will only result in a max of 0.5c lower temps and that can not increase performance even 1Mhz..A chip at 37c can not overclock any better then if it was at 37.5c . . So just set it up as eaily and efficiently based on tubing issues.
Also Using Y Fittings reduces flow and should be avoided.And I hope you are using a dual 120mm rad because that will handle 2 GPU and 1 CPU ,I know this from experence running 2 Xeon 2.4 @ 3675 each and a 6800 ultra.