There are scattered reports of lagging on iOS 11. There doesn't seem to be a clear trend or reason why but I would surmise that iOS 11 is not up to snuff just yet. I would back up the data and try a hard reset first and maybe even a full DFU restore to see if that helps.
There are widespread reports of Touch issues on the iPhone 6S and to a lesser extent, the iPhone 7 when they have aftermarket screens installed. This wouldn't affect you directly. I wrote up a blog post on this last week, you can go check out my profile if you're curious. Hopefully not breaking any rules here by saying that.