Study time advice

This is a very difficult question to answer. Personally I have found financial accounting easier than management accounting and have had to take P1 and P2 several times. CIMA I believe has stated 200 hours per subject but I can say for those two papers I have probably done quadruple that amount per subject.
If you enjoy management accounting and find it easy then obviously it will be less time. The exams are time pressured and having studied the old syllabus, the 2015/ 19 syllabus requires you to really know your stuff as the pass mark is 70%.
I am not familiar with AAT so will you have all the certificate exams to sit?
Re the Operational Level and Mgt level CIMA advise you to attempt the E paper, then the P paper and finally F.
I have studied via distance learning. The advantage is you can practise the areas you are not familiar with. If any subject feels like it takes you too long, then I definitely encourage you to use a support package with tutor support. It may be costly but it will save you time and energy dealing with hard areas on your own.I hope this helps and good luck!