Might want to get your phone checked out then, cause I have it installed on my ancient iPhone 7 and it‘s smooth as butter. It was laggy but the first restart after installing fixed any performance issues.No iPhone 12, I am not willing to install beta on my primary phone. But iOS 15 is lag fast on iPhone 7 (I know it is beta). It is four day now, so don't tell me it is still indexing.
Although I like new Safari, but it is pretty laggy. Lot of blank pages when scrolling, pages will refuse load. Phone runs very hot all day and battery life is bad.
I have restored to iOS 14.6, much nicer experience.
Again, I know it is beta and I am not mad... I am fully expected bad experience...