Which Ram should I get?

Why are you not sold on the Trident Z? It's practically impossible to get better memory, especially if you are going with a Samsung B-die model within the Trident Z family which would be highly recommendable.

There are Corsair Dominator modules that use the B-dies but they are generally a bit more expensive than G.Skill for the same or less quality.

Any Corsair or G.Skill 3200mhz module other than the Flare-X modules should work fine with that build though.

Are you going to be planning to add sleeved cables to the PSU later on, or sleeve them yourself?

Are you going to be overclocking the CPU?

Do you plan on overclocking the memory, or tightening down the timings, or just running it at it's XMP profile?

Also, looking more closely, I think you want a higher end CPU cooler for that 6/12 processor. Minimum I'd recommend would be the Cryorig H5 or Noctua NH-U14S. Some kind of decent quality 140mm cooler. 120mm is not going to give you enough headroom for any decent overclocking at all, and might even be rather borderline for stock operation if you don't want it running at high speeds a lot.

It's VERY, VERY hard to beat the Maximus Hero boards without paying significantly more. In the mid range, the Z370/390, or any gen, of the A series boards are good choices with MOST of the features found on the ROG boards, but the Hero has most of what the very high end Extreme and similar boards have including usually the same sound chip, replaceable DAC, etc.

They also have very good power phase, high quality, good looks, many features and header options. As usual, that would be my go to. The Gigabyte boards are high quality, but having just swapped a Z170x-Gaming 5 (Almost identical to the gaming 7 in the bios and elsewhere) for a Hero VIII, even this late in the game years after it's release, it was like going from night to day. The Gigabyte boards tend to not have as good of granularity in the bios. DRAM voltage only adjustable by .020v increments instead of .005v increments like the ASUS and ASRock boards. That pretty much translates throughout the bios.

Better fan controls. Intel LAN. Lots of little things that make a big difference in the end.

I'd definitely be looking at either the Hero boards or the ASRock Extreme4 or Taichi.

I'd also forego Z370 and use Z390. Power phase and delivery is supposed to be improved on Z390. There is also supposed to be native support for USB 3.1 gen2 and Thunderbolt 2, although I haven't bothered to look and see if that's true yet or not.

Z390 has TWIN 8 phase power delivery. 8 channel ROG SupremeFX S1220 High Definition Audio CODEC. Kind of hard to beat.

Overclocking should ALWAYS be done manually. Automatic and preset overclocking features should be avoided. The "err to the side of caution with overly high voltage settings" these kind of overclocking features bring to the table make them less than palatable and usually result in a far lower overclock, with much higher thermals, than doing it manually through the bios which is not terribly difficult anyhow.

As for memory, just using the XMP profile is not a bad or unwise thing anyhow. There isn't a lot to be gained, gains are small, tinkering with timings and tightening things up. Mostly, for those of us who enjoy doing it, the small gains are just a bonus.

Also, while the G3 EVGA units are pretty good, for a build of this caliber I think I'd highly recommend at least looking into the Seasonic Prime Ultra units. Especially the Platinum and Titanium models. These units have exceptional, even mythical voltage regulation, ripple and noise levels, without needing to use in line capacitors to achieve it. Other, lower tiered Seasonic and as far as I know, ALL EVGA G2, G3, GQ, P2 and T2 models use inline caps which means if an inline cap fails or if you swap out the cables for an aftermarket set that are individually sleeved, you will sacrifice a fair share of those units rather good levels of ripple and noise test results. If you try to sleeve them yourself, you'll have to cut out the inline caps as they can't be sleeved with them left in the ends of the cables.

Plus, the Seasonic Prime Ultra units have longer warranties, and actually live up to them. Don't get me wrong, those EVGA models that I listed are still very good, but not to the same level by a fair margin.