2GB sticks of DDR3 or DDR4 do not make too much sense unless you are talking about a cheap office machine which only came with 2GB in the first place. As @Dje4321 allready said, for an APU you want to use as many channels as possible (mainly to reduce bottleneck).
If you plan on upgrading later, and you have 4 slots, throw 2x4GB into the mainboard in step one so you can put in another 2x4GB later.
@Mr.Namir Do you want to use SYNC/DSYNC on your ram, dual / quad channeling, do you want more complex timings, or do you not care that much. Filling all the slots full for only 8 GB is a bit of a waste. With 12 you can at least get a 4 GB ramdik but at that poist you might as well also just have 16 so you fill all the slots...
Doesn't matter that much. If you were as insane as me you'd have a boot SSD on SATA or U.2, 2 GB ram, and a PCIE SSD for active system swap. Maybe 2 PCIe SSD's and use a caching setup. It otherwise doesn't matter at all.
Thanks for the reply's I was having a little debate with one of my classmates ( I was more like dying and laughing on the inside during the discussion LOL) before our final and she said something asinine about all the all the memory slots have to be filled so the system can be optimize or some thing thing I kinda zoned out but i did catch that last part fill all the slot with 2GB and I'm like wat?
pretty sure 1/2 the slots available is usually the best answer(something about voltage and whatev it limits oc sometimes if you use all of them.. for extreme oc anyways lol) also you have expandability etc for later unless you want max config or you just cant afford to get one per channel.
It depends a bit on the workloads. Of course X99 there is a benefit of heaving quad channel memory support. But for any other main stream system its basicly dual chanel. And the diffrence between dual or single channel configurations is very minimal in the majority of the workloads like gaming. But of course there are certain workload which would benefit from having dual channel or quadchannel memory configs.