The general advice provided to me, and relayed by me is eyes centered @ 2/3th of the screen. The best advice received and relayed by me regarding posture might surprise you. If you struggle with posture, stop caring about what other people might think about your posture. Changing/Tweaking posture all the time might look bad, but it also tends to mitigate the effects of being frozen in bad posture(!) The health impact is too significant to ignore.

Yeah I think the only ergonomic advice I believe anymore is that there does not exist a position that is ergonomic to sustain for more than a couple hours. Humans are not evolved to stay stationary, few mammals are really.

Also use a chair with at least “multi block” (changes seat/back angle when swaying).

I do this too, though mostly out of necessity. I use a 27" screen a couple feet away. To get the top of the monitor level with my eyes I'd either have to lower it so the bottom of the monitor was almost flush with the desk (which my current monitor's stand won't do anyway), or get a taller chair/lower my desk, both of which would leave my legs rubbing up against the desk underside and my arms at an uncomfortable angle for typing.

Either I have an abnormally short torso, or that advice was written back when most people were using a 14" display.

I switched to a VESA arm so I can put the bottom of the monitor flush with the desk and leaned back at a bit of an angle. It’s fantastic.

Indeed. AIUI your head needs to be back, chin tucked in, which means looking down a bit. If you're looking level or up you're going to be sticking your head out a bit