[Long Haired Git]

But not all components need the same amount of cooling, so as long as you align you will be fine (I'm a poet and I know it).
In your example, however, you have a GPU block in one the three branches, and then a bunch of stuff that doesn't need to be cooled much. I'd much rather you have the MOSFETS and the SB and NB in the 1/4" loops than in the main arm. It will make it easier to plumb with the thinner tubing too.

Lastly, resistance is approx equal to the square of the velocity. So, if you have multiple parallel paths then the resistance of your blocks will be greatly reduced as the flow rate through them is greatly reduced. So, if you manage to equally balance all three branches, each will get 1/3rd of the flow rate of the main arm. For a CPU or GPU or any other large wattage temperature intollerant device, this would be a bad thing. For HDDs, mosfets, ram, SB's and NB's however, its quite sensible.
BladeRunner's silent rig comes to mind.

Me, I'd have:

Res->Rad->CPU->GPU->Manifold1_in
Manifold1_out->SB->RAM1->MOSFET1->Manifold2_in->Manifold2_out->Res
Manifold1_out->NB->RAM2->MOSFET2->Manifold2_in->Manifold2_out->Res
Manifold1_out->HDD1->HDD2->throttle->Manifold2_in->Manifold2_out->Res

Where a throttle is like a thumb-screw impedement to the flow to enable the flow to be reduced through this branch to the point where all components get the cooling they require.

If, as you say, you do get a 2nd GPU block, then you may look at more paths etc as required.

To reiterate: Having more flow to one branch than another is not a bad thing if the low-flow branch has relatively low wattage and temperature tolerant devices on it.