I've had a fair bit of experiance with this,
Flow splitting can work well especially when you get to three or more blocks in the system.
I've got seven, so my system is a little different, but I'd say a 1/2" cpu block inflow barb and two 3/8" outlets each suppling one of the other blocks also fitted with 3/8" barbs would work fine, and should give less overall flow restriction to the system and most import block.... the CPU.
