Check your free storage, in my case having 4gb free space on the storage lead to huge performance lag. Having 8gb+ free storage on my iPhone resolved the lag issues.
I have a little over 10gb free.
I honestly think, and this is complete conjecture on my part based on history, observation and experience, that it takes a while for the new iOS to “work its way through the system”... best way I can describe it.
The first couple of days I wasn’t getting any more than noon before having to plug in. Now I’m getting 3-4pm again. Consistent usage, every day.
Now, the lags seem specific mostly to things like after I plug in, I have to hit the home button repeatedly, and wait between presses, to be able to open the phone. Little things like that.
This forum is one of the problem apps... scrolling is very jumpy and slow, not at all smooth.
There are several apps that require waiting between touches... but I accept that may be the app.
Not all issues are 3rd party app related. When I open Messaging, I sometimes have to wait a second or two for the keyboard to come up... there is just a blank white rectangle there for a moment.
Sometimes when I type, I can get several words typed out before they suddenly and magically all appear on the screen.
PS... it’s 11:49 and I’m at 20%