Hello to all from an OC'ing ghost from the past!  Well not yet a ghost! But its been a long time since I decided to build a new rig...  My old OC'ed Monster is still AMAZINGLY hanging in there, and I use it ever day at full OC's settings and it runs like a champ!!! The old rig is the eVGA X58 e770 Classified 3, i7-990X, 3 Way SLI-580 GTX Hydro Copper GPUs, etc. With Processor, South Bridge, North Bridge, and GPUs all being cooled using the external Koolance ERM-2K3U.  This system is still ticking and runs GREAT OC'ed at 4.72 GHz!!!!  But recently I decided to get a GTX 1080ti FTW3 and didn't want to tear up the old rig since it is still AWESOME! So I decided to get my feet wet on a new build using a Z370 setup.  That being said, I first started out with an ASUS Prime Z370-A (it was an open box ay my local Microcenter and I got it really cheap), i7-8700K, Corsair H100i v2 for CPU Cooling and the GPU is on Air and using G.Skill RipJaw DDR4-3200 XMP RAM, and I paired it wit ha Samsung Ultra Wide 4K 49" QLED Gaming Monitor.  I overclocked it and using the built in 5000MHz OC option in BIOS, I overclocked the GPU with a +50GPU Clock offset, then a little tweak here and there and I got it running great at 5200MHz.  Using Unigine 2 Superposition for benching, I was able to easily get a score of 9915 at 4K Optimized.  But being the fact that I'm not an ASUS fan, and have always used eVGA components I purchased a Z370 FTW and swapped out the remaining components to use the new mother board.  But after several attempts to hit the same or better score I got when using the Asus board, I can't seem to get my score past 9824. Any one have some quick ideas on getting to a 5200MHz - 5400 MHz. 
 
Thanks in advance!   
 
Update:  My OC is stable at 5200Mhz and I'm hitting 9900 score.  So I think tweaking a little here and there is working.  I'll keep updating as things change!
 

Be carefull with the adaptive voltage, it can end up boosting it way over what you set. It's showing 1.504v in your screen shot. 

I was having the same issue with mine, and my score had decreased significantly untill i went back to manual.
difference in a 5ghz overclock on a 8700k
 
Cinebench Scores:
adaptive voltage would give me a mid 1500 score: something like 1545 and would boost the voltage upwards of 1.48v - 1.49v
 
manual voltage would give me a little over 1600 score: something like 1635 and the voltage was set to 1.345 and would usually stay around 1.32v during benchmark