I'm having a lag problem on unlock too (64gb 6s Plus). It actually pauses as the icons are dropping down to the screen with the zoom animation, for a second or two I have giant icons showing as it freezes when they're coming in. Then they land and all good.
Concerning thing is, this is my 2nd phone. The first had a problem with the earpiece sounding blown or something so I got a new one. I had no lag at all on the first one and I'm only noticing it on this one after restoring from backup, makes me worry that this is a hardware problem. Haven't tried setting up as new yet...
set it up as new.