I would go for one big loop with all the radiators you've got. I think it's a better idea to use all the cooling capacity for all your components. Especially 3 titan x's (if your sig is right) are going to produce way more heat than your cpu.
From my experience with watercooling, it doesn't really mather in which way you set-up your components. The only thing that you have to bear in mind is to place the pump directly under the reservoir.
To connect all those fans, personally I would go with a fan controller. You can use those fan splitter cables too, but first check the maximal current that you can draw from your motherboard's fan header.