Your correct the Asus support site will list the memory kits that were tested and work for your motherboard in the QVL.
When shopping for G.SKILL memory kits listed in your motherboard QVL you can also use the G.SKILL site to cross-reference memory kits, and click on the QVL tab in the memory kit Overview on the products page, clicking on the QVL tab will drop down a list of motherboards just click on motherboard manufacture and your chipset, it will show if the memory kit is compatible,.. as G.SKILL also does in house testing.
https://www.gskill.com/products/1/165/Desktop-MemoryThe last three letters are the modules series, and or heatsink color,.. GTZSK is Trident Z memory with silver & black heatspreader, GTZKO is black & orange, GTZKW is black & white,.. and so on they have a ton of colors, and series,.. the GVK are Ripjaws series,..
Personally on LGA 1200 system for 32GB total I would go with F4-3200C14D-32GTZ kit which would be 2 X 16GB CL14 3200MHz modules,.. and you can overclock them if you feel you want faster speed, those modules will easily OC to 4000 CL19 with LGA 1200 system. For normal usage running 3200 CL14 you should be good to go.
https://www.gskill.com/product/165/168/1536199461/F4-3200C14D-32GTZTrident-ZDDR4-3200MHz-CL14-14-14-...