Just updated to 10.3
Using a complex wallpaper, all of my apps stutter when opening and closing now... on 10.2.1, it was just Safari and Mail that would do that.
However, if I use a simple gradient, it's smooth as silk.
Here's one of the wallpapers that makes it stutter
and here's a wallpaper that's fine:
I'm using an iPhone 7 Plus by the way and the display is set to "standard".
I know it sounds a bit weird that a wallpaper would make a difference but in my case it does make a difference. I would say only a handful of wallpapers make opening and closing apps smooth, but most of them will make them stutter (even the Apple wallpapers)
Also, it doesn't seem to stutter until you change the wallpaper from the default one, to a custom one. Once you put a custom wallpaper on, it starts stuttering (unless you get a good wallpaper like the sunset one I posted).