Dave,
In the olden days I used to always have my chin on my cue (hence eye to cue angle consistent), with a scab on chin to prove, when doing 6 hour sessions daily.
Since playing US pool I developed a higher head position and that has freed up varying eye alignment and experimentation thereof.
I see a lot of the best potters in snooker are pretty much one eye over the cue, some left and some right. I've had some success with both and can also learn to perceive lines ok from mid positions if needed.
Some days I get the feeling that X eye alignment is the way to go, but such tendencies vary.
If one picks the shot line, or visual as in CTE, from back in stance, it seems the eye to cue position is less vital.
It is a fascinating topic, certainly plays into visualization. The long straight shot on a 12' snooker table is a perfect example. The geometry is easy, CCB to COB, but it's very hard to perform consistently. From baulk it's probably an 8 or 9 from 10 shot for pro snooker players. My best was 18 from 20, with an average around 14 when playing lots of snooker.
imho, 80+% of misses were alignment based, not stroking errors. And, even though the geometry was simple, it took intuitive judgement (feel - though I don't like the term), to place the bridge along the CCB to COB line.
Colin