Does speed help? That's a very broad question, as "speed" or "fast" isn't defined. What is fast, is 280 fps or 300 fps fast? They are both "fast" or "slow" relative to the environment. 280 fps would be smoking at 45 lbs and 25" draw with 5 grains per pound. A bow that is IBO rated at 300 fps is considered slow.
I have a short draw and my "3D" Cougar has to be "right" to get it in the 280's. This same bow I've used at Lancaster in '07 and '08 so it's also a "spot" bow. It's shot many 58+ X's over the last couple of years. This bow is accurate and I shoot it well. But if I could get it to 300+ fps for IBO shoots I could and would use the 20 fps, I'm sure I would score higher!! I've shot with guys that were shooting 305+ fps from the same stake as I. 20 fps difference is significant.
Many top ASA shooters have IBO bows or set ups that go 300+ fps. They wouldn't be going faster for IBO than ASA if it didn't help them.