It'll be the same on 8th gen as the silicon is identical at least as far as this is concerned.
You should look at timings as measurements of cycles rather than absolute time even though they are closely related in as far as DRAM performance is concerned.
There are always going to be different levels of DRAM tuning you can get into. There's no need to get into anything past X.M.P but if you do, you have to divorce yourself from only thinking about the primary timings.You're not concerned about the default turbo frequency of a CPU, only how far you can overclock it. So too does this apply to DRAM overclocking. Knowing the default primary timings is great and you can discern plenty from that. However in getting performance out of the memory, you'll need a lot more than the XMP timings as they aren't as important initially.
At 3,600MHz on a DC setup you should want to get as close to 57.6GB/s in memory bandwidth. Typically you'll find you're not even in the 50/s but rather 45 ~ 47GB/s
timings as mentioned above outside of the primaries is where you want to look. Consider the tertiary timings in particular as they give some boost to effective bandwidth, bringing it close to theoretical max. In AIDA64 you can gain anywhere between 2 to up to 4GB/s sometimes in each of the READ, WRITE and COPY tests while lowering your latency and not compromising stability (as you largely left the primary timings as they were. These determine stability over all other settings or at least in priority).
Also realize whatever frequency you're aiming your sights on, consider the total latency (in time i.e ns) of the transaction, use this site -
Ram Latency Calculator
to help you do this.
4500 C18 = 8ns
4200 C17 = 8ns
4000 C16 = 8ns
As you can see, in terms of absolute latency, all these frequency and CAS Latency combinations are the same. A motherboard and DRAM combination or either one exclusively may not be able to reach 4500MT/s for example (2250MHz), but it may very well do 4200 or even 4000. In which case, it's even more important to tune the sub timings. You can't make up for the bandwidth advantage the other frequencies and straps have, but you can match the latency and in a number of programs this is actually more important than outright bandwidth.
Try bring down tCKE to 6, along with tFAW (24, 23 and even 16 should be fine if you're adventurous), tRFC (You can usually bring this down to 350 or so without issue on OC boards, but if you're using 16GB DIMMs or 4 DIMMs 560 is alright) You could also try tREFI I usually set this to AUTO as it doesn't impact performance, but can compromise your stability. How to set this is also quite random form the outside as boards deal with this setting in differing ways). 15,600 is alright, 17,400 or what have you, even 65536 is ok. Again for stability more than anything.
This program can help as well in not only testing your memory settings, but doing so quickly (It's much faster than HCI or any other program, by some margin. -
RAM Test - Karhu Software). Can pretty much test to 3,300% and be sure of absolute stability in around 41min depending on your CPU.
Finally. how DRAM tuning is important is simply because that's the most measurable or meaningful way in which motherboards are different. The rest is mostly BS, but making a board that's tuned well for all sorts of kits is tough and a constant challenge. As such they would rather place more focus on some other 'features'.
