This pretty much falls in to the "what's the best table" "what's the best cue" "what's the best chalk" category. Basically, it is whatever works best for you. Everyone looks at the OB & CB as part of their aiming process. Where your eyes are during your stroke is a matter of personal preference and you will find people on both sides of the argument from beginners through pros.
I think everyone can pretty much agree that stance and set up dictate aim to a large degree and if you don't land the cue tip exactly where you intend to on the cueball you will not get the intended outcome.
Sometimes it helps to look at a situation backwards, instead of saying "what do I need to do to make a shot ask "what can I do to miss the shot" with the answer being either "pick the wrong line for the cue ball to travel" or "don't deliver the cue ball to the correct line." The former is bad alignment or not understanding how the object ball reacts to the cue ball & looking at cueball or object ball last is not your issue. To me the latter is a bigger issue and it gets exponentially bigger as you increase the speed of your shot.
You need to understand what aiming means from a standpoint of how & where you need to deliver the cueball (angle, speed & spin) which is table knowledge and physics and not dependent on execution other than delivering the cueball. Where the rubber meets the road is actually delivering the cue ball accurately and the prerequisite to that is being able to deliver the cue tip to the exact spot you desire on the cueball. If you miss the first step the rest doesn't matter.
If you have a perfect stroke, just set up and fire with your eyes closed because your set up and stroke are perfect and you will rarely miss or get out of shape.
