Is this for injury prevention, or technique for max strength or hypertrophy eg upper pec development?
A lot of what works for individual people is based upon the persons shoulder structure as much as technique. What works for one person can cause pain in another.
For powerlifting/strength work I suspect(because its not my field of expertise)scaps back and down, work the best for most people. Trying to put them in your back pockets of your pants. Elbows close to body, touch bar/dumbbell to lower pecs.
If your joints can handle it wider grip benches, touching the bar higher up the chest can be better for some in terms of pec hypertrophy. This usually means your shoulders are in a different position but I would still have your scaps flexed back and downwards. If you let the scaps float too much(unflexed) it can cause impingement.