Annoying lag while searching in iOS Safari
I had the exact same problem! I got the following solution, courtesy of a call to Apple.


Go to Settings > Safari
Select "Clear History and Website Data" (note: this will wipe your history on your phone and any devices that sync their Safari data with your phone's over iCloud.
Change the Block Cookies setting to Always Block.
Close Safari from the app switcher.
Change the Block Cookies setting back to Allow from Websites I Visit.
Enjoy your non-laggy Safari!