The only variaiton I’ve found that works for me on speed day are pin presses right off my chest. Concentric only benching builds a ton of speed for me. Any kind of board work always felt more like stroking my ego than actually helping my bench.
That being said, switching bars as often as you can stand builds strength from many different leverages. I’m lucky, I have 4 different bars I can bench with: a 4inch cambered bar, fat bar, slightly obese bar, and a competition texas power bar. Start adding in different chain and band combinations, hand placements, and different slight inclines, all of a sudden, I have about 1,000 different variaions to pick from.
The trick is figuring out which ones will actually help your speed on bench… usually it’s the one you like the least.