I'd say it depends on how impactful the change is. You first sculpt in Dynamic Topology to have a lot of freedom to deform and radically change your shape. If the changes are subtle enough, such as you are describing, then I'd say the retopo model is good enough to work on for those changes. And yes, what you do on this stage of the process will impact what comes later, but if you're happy with your retopo and you only want to refine certain traits, after you tweak and move on, you shouldn't worry about the fact that you refined some things right now, once you call it done you can move forward.
Omar and Adrian are absolutely right when they say "it depends". The examples you've mentioned:
my cheeks is not high enough, or my nose tip is too big, or i want a smaller lips
I consider those broader proportional changes. I would likely make those changes after a full retopology and transfer of sculpted detail. Because you could jump into the edit mode, select the verts of the mouth, and scale up with proportional editing for smooth falloff. All your sculpted detail will follow suit, which I find to be a very effective way to make proportional changes since edit mode is much more intuitive.
Just be careful about adding or removing verts in edit mode with a multires modifier involved. That can cause big problems. But proportional changes are usually safe.