For most of my PL career I was mainly a bench specialist. I always squatted and DL'd but not with real focus. For me, I found that to improve my BP, I had to BP. I would vary my assistance work, and I would vary my speed work between full range bench with chains, or full range bench with bands. Lockout stength you get from boards, pins, etc... is important, but if you cannot explode the weight off your chest, it does not matter if you can lock it out or not.
Some of my most consistant gains came when I went through a few cycles in which I used chains on my speed and heavy days. On my heavy day, I would only use about 20lbs, which seems light, but I just wanted the gradual increase in resistance it gave me to help me lockout. On my light day, it was heavy chains and moderate bar weight.
For me, the more movements I added, the less gains I saw. I had to keep it simple. It was more of a blend between PL type training and BB training. I was also under 25 years old at the time... so maybe anything would have worked... My best raw bench was 455 at 165lbs.