Just so you don't feel like you are being ignored.
You have asked some pretty wide ranging questions, so You are going to get some wide ranging answers.
1. Best pad in different situations.
Cutting pad with compounds, IMO best used only with a rotary.
Polishing pad with polishes
Finishing pad for sealant or wax application.
In my case, I use a different pad for each product I use.
Lots of choices as to brand and type of backing plate system to use.
2. How to clean the pads?
Some wash them, some use a soft brush to brush the dried product from the pad. I have done both. Right now, I'm back to washing them in soap & water. Your choice.
3. How often do you need to clean them?
For me, it is after each days use.
This isn't much, but it is a start. Keep reading and asking questions.
Charles