I think it's most common for the foot to be straight. With the big toe and heel aligned it's going to have a rotation outwards (at least mine does when I try it). If one accepts the general rule that the foot landing goes from front to back (ball to heel) and outside to inside (little toe side to big toe side) then a foot placement that is more straight ahead intuitively seems to support that. I don't know that a small rotation one way of the other would matter much, and we all have different feet so I expect there is variation here.
I would certainly agree the foot should be relaxed. You shouldn't have to force your foot one way or the other if it's not landing there naturally. However, I'll share bit of a story here which may (or may not) be helpful. When I was suffering from a bit of ITBS I had one of my kids take a video of me from the side and from the front and back while running....just to check form. I noticed from the back view that my feet were landing almost on a line.....which is to say, if you drew a line on the ground, both my left and right foot would land at least partially on the line. I thought about this a bit and decided to try to consciously create a few inches of separation between my feet as they landed. To do this I found I just had to relax and open up my hips a bit. That got me to 6-8 inches between my big toes as I ran. This, I believe, also helped my ITBS as it got my feet and hips better aligned, and also removed a bit of foot rotation outward. Anyway, it's helped me out quite a bit. Not sure if it's helpful or related to your question.