I just upgraded from a mini to a mini 2 and almost returned it but iOS 10 made it brand new again. The A7 may be getting old but the chip was ahead of its time and should hold up. Yes ram has it limitations but overall the device feels fast still and iOS 10 made browsing in safari doable. iOS 9 was a nightmare for some reason on the mini 2. Even the keyboard is snappier when going to type in a web page address. I'm glad you like your mini 4 though great device !
I can believe that. My iPad Air 2 never felt like a slouch, but iOS 10 makes it feel faster than it was when I got it. I'm eager to get the final release on my iPhone SE and iPad mini 4, but I'm also curious how the iPad mini 2 would handle it. I'll probably never find out though.
It's nice to hear that iOS 10 is actually improving device performance. Maybe people around here will stop going on about how updates cripple devices and you should never install a major update.