Windows just because it's the only OS I actually know what i'm doing half the time, and licenses are easy to come by. I do NOT plan to use computer as a normal desktop. It will trickly be the home network hub and nas.
So far I thinking of using a Z270 GAMING M6 AC with a 6700k, since i already have that mobo, cpu, and a compatible power supply/case. I only need ram, the ssd/hdd drives, and of course the lan switch card/s and possibly a WIFI solution.
I was thinking a 120gb ssd for the OS in a m.2, with 3-5 hard drives, I haven't yet decided on the exact makeup of the raid, and this would be my first time building up a raid array as well. (but i'm thinkin raid 1, raid 10, or raid 5, as I am not to concerned with write performance, but more worried about read performance, as the nas portion of this build will be for storing a huge library of games, as well as movie and video files which will have multiple users reading the data at once, but NOT writing data.)
I was also thinking between 32gb of ram, with 24gb for the NAS, and 8 for the router. Other than the hardware, i also need to learn how to setup and asign out the hardware for both mochines in VM.