I appreciate all the responses.  I have not decided yet which MB to get, but you all are helping me think through this.  I will definitely research more and figure out which one has the features that I will need. 
 
I definitely want one that will have the option for a M.2 bootable PCIe but one where the M.2 does not take away one of the SATA 6 ports; not all boards have these options or they require additon add on cards to make it work.
 
I have come to believe that getting the best possible MB is as important as the CPU.
 
My local Frys is just sold out of Intel MBs right now, but Newegg does stock a growing variety of Z370 boards and has helpful reviews.
 
Again, thanks for all the advice and discussion.
 
C2

Since you mentioned the SATA ports, another thing to consider is the case itself. I didn't put much thought into that part and got a case that is literally wide open in the MB area (top section), and has the liquid cooler along the front panel area (at the expense of NO drive bays up top). The bottom section is enclosed so a cooler rupture cannot get the drives or P/S (upside), but that bottom enclosure can only fit two 3.5"drives (or 4 SSDs) in it. The case is smaller than my old one, but set up much better for cooling at the expense of drive bays. If I want to use all 6 SATA connections (I am only using 2 + an NVMe M.2 OS drive), I would need another case.

I have a very big case (5 x 5.25 and 5x 3.5 slots). 
What I am now realizing is that I do NOT want to have the m.2 in pcie to take awy sata ports, but I don't care if it steals from any of the PCIe3.0x16 lanes.  I really don't need the PCI3 3.0x16 because I am not running big GUI cards.  I will just use the onboard GUI on the CPU chip.  I have read that there are some MBs that borrow the lanes from the PCIe3.0x16 and not from the SATA ports.  However, most of the MBs seem to take away one or even 2 of the Sata ports.  
 
I run 5 Sata HDs and want to keep them.  So finding a MB that will have M.2 in pcie mode that will NOT steal away any of the SATA ports is most important.   
 
The problem is that the ASUS and ASRock websites do not always make it perfectly clear where the m.2 steals from.  Even downloading the pdf manuals does not always make it clear if the m.2 borrows/steals the SATA or the PCI3 lanes.
 
I would even get a more expensive MB with extra PCIe3.0x16 slots, because I would not need them for anything other than using the m.2 to take their lanes.
 
Still, thanks for all the help.  The more I read, the more confusing it gets, but also the more I am learning about these new z370 MBs.
 
Thanks again for all the help.
C2
 
[[EDIT:  I just realized that I would be able to add a  SIIG M.2 NGFF SSD PCIe Card Adapter in one of the PCIe slots which would allow the use of the M.2 M key pcie card.  This would add the M.2 without taking away any SATA lanes.  Now I can focus more on a Z390 MB with the best overall stability and other features.  Thanks again for the help you guys have given;  You really do help so much! ]]

I’ve just finished my build based on an ASUS Z370-A with and i8700k.

This is a good starting point for the Z370 comparisons (17 MBs compared to the same test). If you click on the comparison tab, it opens this link (if you like the eye chart version). The benchmarks are all the way at the bottom.
 
I got the updated ASUS ROG Maximus X Hero (Wi-FI AC) when I built mine, but that one is not listed here. Many of the parameters are very close across all boards, so do not get distracted by details as much as the high level features available.
 
Another side note is my board shipped with the stock BIOS, which has had two updates since release. The new BIOS benched 10% above listed values after installation with no overclocking (I have since bumped it up to 39% but didn't re-evaluate it yet).

mettelus
This is a good starting point for the Z370 comparisons (17 MBs compared to the same test). If you click on the comparison tab, it opens this link (if you like the eye chart version). The benchmarks are all the way at the bottom.
 
I got the updated ASUS ROG Maximus X Hero (Wi-FI AC) when I built mine, but that one is not listed here. Many of the parameters are very close across all boards, so do not get distracted by details as much as the high level features available.
 
Another side note is my board shipped with the stock BIOS, which has had two updates since release. The new BIOS benched 10% above listed values after installation with no overclocking (I have since bumped it up to 39% but didn't re-evaluate it yet).

Thanks for this.  I had not seen this benchmark comparison.  The second link is also very helpful by showing all the details in a side-by-side "chart".  
 
Everyone has been very helpful.  Thanks again for all the help.
 
C2

Just put a build together for my nephew using this one:
https://www.newegg.com/Product/Product.aspx?Item=N82E16813132855
 
VERY easy build.  The Noctura cooler works GREAT! and is silent.  He also got a Fractal Design case that had VERY quiet fans.  In the end his i7 8700 with 16GB RAM is quieter than my studio box (AND A LOT FASTER!)
 
These motherboards are very well laid out and easy to make a nice install.  The fractal case is nice because the wiring is run below the motherboard.
 
The ONLY drawback with his entire system was that the case did not have a 5 1/4" slot for the Blu-ray drive.
 
Here is the case:
https://www.newegg.com/Product/Product.aspx?Item=N82E16811352070&ignorebbr=1
 
 
Here is the cooler (it is Large, but EASY to install!)
https://www.newegg.com/Product/Product.aspx?Item=N82E16835608045
 
BTW, the second fan is optional!!!  You only need the one between the coolers.  That is all we used.
 

My build is an ASUS ROG Maximus VIII Hero.  I tried the Noctua cooler but its big and my CPU temps idled around 40C.  I replaced the Noctua with a Deepcool Captain 120EX liquid cooler and the temps dropped to around 31/32C and it was as quiet as the Noctua.  I'm using a "BeQuiet" case that has room for two CD/DVD drives and it too is quiet. 

I've used Asus, Gigabyte, AsRock, and Intel.  Never had an issue with any of them.  I still have my socket A stuff in a closet. I never spend over $150 on a board since I don't need a lot of bells and whistles. 

my MSI B250M is still rockin', a month into the new build.