Mine is fine for playing video on iOS 10.True as long as it plays video without stuttering it should be ok.
Scrolling while surfing is definitely an issue for the lag. For example, going on MR front page and scrolling down to see all the articles, the screen will go white and the webpage will eventually pop up. It seems to be worse for scrolling back up to the top.Rest is just books and surfing
I think the Mini 2 is behaving like it is low on RAM and it is page swapping everything. It was much worse under iOS 9 than iOS 10, but it ran perfect on iOS 8.