Regarding Dell/Samung NVMe 1725a 2,5" SSD drives.
Have you tried with Windows Server 2016, as we get VERY POOR performance. Due to only standard device drivers from Microsoft, for this OS version. Specs says 700.000 random read IOPS, we get 1/5 of this, about 120.000. On an five year OLD FusionIO card, we get +400.000 :-s