I use mine on my 6s, and I love it! Since it works so well on the smaller 6s, I can imagine that I'll love it even more if I go for the 7s Plus. Now that I have one and like it so much, I can't imagine getting a larger phone and not having one.
I bought an original Popsocket, and those can be removed and repositioned without compromising the sticky stuff. I also bought a few Popsocket knock-offs from a kiosk at the mall and those work exactly the same as an official Popsocket. In fact, I think the knock-off one is better because the image is on the plastic round piece, whereas the original Popsocket feels more like a paper image stuck to the plastic. My original one shows quite a bit of wear in the short time I used it whereas the image on the knock-off hasn't shown any wear at all.