Are you building this for competitive overclocking? Or because you plan to do a FULL custom loop?
The Apex is simply for competitive overclockers, nothing else, which is why it only has two DIMM slots. The Formula is for people with either intentions for full custom loops or more money than brains, in most cases. I'm not saying that's you (But I AM saying it's some people out there who are simply looking to impress their rich friends), but honestly there are very few reasons to go with either of these boards and both of them generally involve extreme levels of overclocking which honestly, has very little relevance on 12th and 13th Gen CPUs. Well, maybe some but not as much as past generations, unless you are intending to build a full loop.
There are exceptional boards that are much cheaper than either of these, even factoring in the purchase of all the hardware to do a full custom loop from scratch.