It's good to start lighter when your technique is off. But don't be too scared to move towards heavier as well. Take your time , but don't get stuck on the small details that aren't really putting you under a risk of injury. Nobodys technique is ever perfect, if you are doing things right, you are honing your technique in every rep of every set, no matter the intensity. You do the movement light because it's easier to fix, there are no intenisty-induced faulty movement patterns. Using video recording is a great way to see the truth in your own movement. If possible, film your bench and analyze it.
Whenever someone is aking about Bench pressing, I like to refer to Dave Tate. And more precisely, "You think you can bench" -video seires in youtube. It's putting together so much information on form of the bench, and the same tips are seen everywhere on bench articles and seminars.
On bar path, especially when it comes to heavy benching, I think it's best to make the Range of motion as small as possible. Which means that the bar should go the shortest distance. No suprise there. It's pure logic. How do you achieve it? By making the bar go straight. Not in any angle or with curves, but straight down, straight up. Only on set-up and rack should the bar move to other directions than up or down. That's the way I've learned and that's how I bench every time.
I will absolutely progress in intensity.
Regarding the bench "groove." I posted above his argument for not a perfect vertical movement. He writes quite a bit regarding how it's bad for the shoulder. You are not buying into this? He does say that "Moment Arm" is a lifting inefficiency, but that it is a necessary evil for health.
I will look for the videos, thanks.