I haven't taken the PMI-ACP, but I am familiar with the material and it is distinctly different than the PMP exam. You'll need time to study the concepts of each exam, individually; there may be some overlap, but its not a winning strategy to study for both at the same time, even if you do meet all of PMI's requirements to take both tests. Focus on one first and then do the other after.
As for studying, I personally recommend a time horizon of at least 3 months for the PMP exam. This gives you a moderately paced schedule that won't destroy your personal life but still ensure that you can pass the test on the first try. If you are interested in my study plan, its here: