You bring up several excellent points.  The first is that when there isn't much good scientific evidence, then doctors will rely more on their experience and those experiences may differ.  Also, sometimes we just disagree on the science or how much to weight certain studies. 

So, on the exfoliation issue, I've never any science on this but, in my opinion, it really depends on your skin type.  If you have younger, thicker, oily,  or acne prone skin, you will be able to exfoliate more often (maybe even daily) and not get irritated.  If you are older, thinner skinned, dryer, etc,  less will be better, possibly even only once a week or less.  I think this is a more common sense thing.

On copper peptides and wrinkles, there is some science here but it's not great, in my opinion. I'm waiting for more data.  It won't hurt you so if money is no object, maybe try it.   There's still disagreement on cell growth factors (fibroblast media with EGF as one component).  In my opinion, the science is good enough (but not conclusive) that I recommend these as an advanced option after the basics of sunscreen, retinoids and antioxidants.  They are expensive.   DMAE - maybe I'm missing something here - but I've not seen any good science on this.   Hope this helps.  Dr. I