2012 Macbook - A1278 - MD101LL/A*

[Squeechums]

Hello! I just have a quick question that hopefully someone can assist with.

I have a 2012 macbook - A1278 model MD101LL/A
Right now it has 2x4GB RAM
I just purchased 2x8GB sticks, and I would like to possibly use 1 of them with an existing 4GB chip to make 12GB.

A: is this ideal? Do I even need to do this, or will I never need more than 8GB? Will I not notice a difference?
B: Is it even possible to do this with the dual channel?

Thanks so much!
PJ