120Hz will make it unnoticeable to most people but some few will still notice it even with those. To really solve the issue for everyone need to go to 240hz panels. When people complain that Apple used cheap panels, they mean they didn't use the 120hz panel that they theoretically could have for that size. Will probably see that on the 7.
No, they just need to just use the Mini 5 panel then it is ok for most people. Using a vertical jelly effect panel for Mini 6 is just for cut cost. Just like they make a small white cloth and charge for $19, they just want money.