If you take two drugs both metabolized by cyp450 3a4, does the better binder raise the levels of the other in the blood, or v/versa or neither?

Depends on drugs: Some drugs induce the enzyme, which means it makes the enzyme break down other drugs more rapidly. Some drugs interfere with enzyme functioning, which means the other drug will break down more slowly. Post the specific drugs and we'll give you specific info on them.

Depends: It depends on the activity; there is a difference between being metabolized by the enzyme, and inducing or inhibiting the enzyme. There are many substrates that have no activity on the enzyme itself. If you have just two substrates, the enzyme is not consumed by the metabolism, so the drugs should not interact with each other, necessarily.