In your scenario you should have both pairs running in dual channel.
For pure reliability issues one single pair is better then 2 different pairs, but since you have matched pairs in each channel you would get the full bandwidth (assuming you put the pairs in the correct slots).
Now unless you are using a very heavy memory applications like engineering simulators, then you wont use 32gb, even power users cant use more then 16gb of ram with heavy multitasking.