Last year, I always had a case on my GS6 edge every time I used Samsung Pay and never had problems.
I only used 3 different cases with this phone, all of them worked fine with Samsung Pay and wireless charging.
This year, I've being using Samsung Pay on my Galaxy S7 edge while the phone is in a case and it works fine.
I have 6 different cases, all of them work with Samsung Pay and wireless charging.
Having said that, there are cases that because of the materials they are made of or because their thickness, might not work with SP or wireless charging.
Sent From the Edge of the Seventh Galaxy