You might have already seen it, but I wanted to share it with y'all. I did not make this chart... Using this I determined (for my build) that G.Skill Trident Z 32 GB (2 x 16 GB) DDR4-3200 was the way to go
The problem with charts like that is they are meaningless beyond a single use case since RAM speed performance gains are not fixed.
Let alone it isn't considering the gains from ranks or interleave or programs not benefitting from memory speed.
If you are gaming all you need is 16 Gb.