Mixture changes with air speed? Wow, that's a new one for me. Maybe you're refering to the prop unloading at full speed straight and level flight?

The pump or regulator will solve any mixture problems. You need one or the other, not both. People have success with both. I personally tried both and the Cline regulator would not run right after a while. It ran perfectly at first and then just would not work right after a while. I probably did something wrong but I gave up and got a Perry VP-30. I actually really struggled to get that working right also but it runs great now. I had to turn it in 2-3 turns (rich) to get it to run right. It's true that the pumps/reg's take a little more work to get working properly but to me it's worth it.