Need Advice on How to Choose a Surgeon?

I was thinking of getting a FUE hair transplant. I was hoping those that have been through it could give some advice on the following. Thanks for your help!  How do you know/verify that the specialist delivered on the number of grafts that he charged you for?

How many hair follicles should be in a graft?  What is an optimal number of hair transplant procedures done by the specialist? Some I called said they’ve done 50. What is a good baseline?

Does it matter if the specialist is board certified plastic surgeon?

I have spelled it out in great detail in two posts here: https://baldingblog.com/before-selecting-a-hair-transplant-doctor-do-your-homework/ just follow the link