That was one of my original gripes with the SO CALLED smooth iOS 10.xx. It is smooth, but lags. The old Sony Z3v I have is lightning fast compared to the iP7+, touch the screen and instant feedback, iOS lacks the ability to forgo all the screen transition animations and do just pure transitions without animations which gives a better appearance of speed. BSD, what iOS is based upon (modified BSD), has always had a tough time with OS animations, seems it carried over to iOS when it was used as a base. When I first used BSD back in 2001 it was clunky to say the least, I have tried BSD from time to time since then, never really equaled Linux proper. In Linux proper, in KDE you can set animation speed, make opening applications fly or slowly open, get the hint iOS.
So you're not alone.
I have a xperia z3 compact as work phone and I can say it was fast two years ago but not anymore. After each update it gets slower and now the camera is a joke and can have a sharp picture on the screen but when I press to take the photo it always adjust the sharpness and often on closeup photos you can't see or reed if I taken photo of a sign or text on a paper.
Must take several photos to get it right.
It's slow when changing apps.
My iPhone 7 is much faster and when I shut of movement or what it's called in setting under aid in settings.
Now I'm not sure if I got it right in English.
Because my menu is in Swedish.
But toggle of movement so screen not use parallax effect and movement is used very little my phone went from fast to much faster.
Was not having issues as it was and now I don't know if I should stay or go back again.
I somehow like how it was and have no need of this extra speed.
Maybe it saves battery when my processor have much less to do[emoji6]
Anyway I can't say that my Sony is anything near my iPhone in speed and not my sons iPhone 6 either.
That phone and my old 5S is faster to switch apps and do things with than this Z3 Compact.
All is running latest iOS and my 7 is on latest iOS 10.3 public beta version and feel it gets only better all the time.
So pleased I went over to iOS on my private phone when the iPhone 5 came and never had any issues like I have had on my different android devises I used during many years.