I've not found any concerns with iOS 15 over previous major versions.
Google Maps has been working fine, and haven't noticed other apps get laggy and lock-up.
I did notice facebook was a bit flaky after initially going to iOS 15, but seems to have been sorted with newer app releases from Meta.
I wonder was it iOS 15 causing these issues or was it the FB app itself? I've noticed similar issues with various apps after previous major releases, again which cleared up with a few app version updates.
I'm using both iPhone 12 pro and iPad Mini 4.