I like a lower 1/3 cowitness. You look through the irons and there's your dot in the lower 1/3 of the optic lollipoped on the front sight. You can look over the rear sight and there's the dot floating over the front sight. Or you can fold down the rear sight and there again is your dot, above or on the front sight depending on your cheekweld. Best of both worlds, optics and irons.
The biggest issue with assembling an AR isn't so much getting the parts together right - it's getting the right parts together. You'll remember the quality of a gun long after you forget how much you paid for it.
US Army 1966-69, VFW Life Member, Retired Geek