Hay everyone, so I'm putting together a system with a x299 dark and ether a 9800x or a 10900x.
would there be any real world benefit to getting faster ram or ram with better timings?  Like say 2666mhz ram cl18 vs 4000mhz cl18 or 4000mhz cl20 vs cl16?
The only thing on this system that will ram depended will be a ram drive with a lot of files with sizes from a few 100kb to a gig or 2 and large file transfers.
I'm guessing its not worth the extra money, but thought Id ask. 
 
BTW I'm going from a x58 system with 24gb of ddr3 in triple channel at 2ghz cl10.

DEJ915
Lower timings and higher frequency will lower your latency which bumps up frame rates a lot so yeah it is a benefit.   4000c16 would be the best from what you picked then c18, the other two I wouldn't even consider.

Yes, but the CPU needs to be able.

Honestly, IMHO answer is "it depends" and it will depend on what kind of workload you will be putting. YouTube is full of various comparisons so you might want to search for ones that fit what you plan to use but from what I have seen you wouldn't be looking at huge differences between "slowest" and "fastest" kit unless slower one is bad pick to start with.

DEJ915
If you want to be cheap and don't care enough to look for results just get a 3600 c18 kit or something.  Overpaying for some old x99 sub 3200 kit is stupid.

Assuming same capacity how much of price and performance difference one would be looking at between CL14 3200, CL16 3600, and CL18 3600?