I don't know where you heard that 16:9 is "more natural to what humans see". That's just pure BS.
If you are leaning in to read the text, that tells me that the have difficulty reading the text clearly. If the Dell is adjusted to the lowest height level and your chair is adjusted to the maximum height then that seems to indicate that either the desk is unusually high or you are shorter than the average person.
When working in front of a monitor for a long period of time, then it is better to be eye level with the top of the monitor or a little lower. Looking up at a monitor for a prolonged period of time can put a strain on your neck muscles I suppose. However, you can also roll your eyes to look up a bit w/o having to actually tilt your neck.