No improvement yet?
.plist files are just preferences. You don't have to delete them, just move them to a different location (moving them to the trash counts). I typically make a folder for each location they came from, so I can return them if needed.
When a .plist file is removed, the associated application or service simply makes a new default one...which can solve problems if a preference has become corrupted somehow.
If pulling the preference files does not help, next you can check for any third-party add-ons. Note that the ~ symbol means
your user name in the file path.
Delete Third-party Add-ons
- Apple Support warns that third-party add-ons can cause Safari to quit, run slowly or have other performance issues. Check the add-ons installation package for an uninstall feature, or manually remove the add-on files from the root-level and user-level libraries in Finder. Locate the following folders in your root-level Library folder and browse their contents for any third-party add-on files. Move them to the Trash, but do not delete them.
/Library/Internet Plug-Ins/ /Library/Input Methods/ /Library/InputManagers/ /Library/ScriptingAdditions
Locate the following folders in the user-level Library in your Home folder:
~/Library/Internet Plug-Ins/ ~/Library/Input Methods/ ~/Library/InputManagers/ ~/Library/ScriptingAdditions
Open each folder and move any third-party add-on files to the Trash. Do not delete them.
Reopen Safari. If Safari opens, replace the files one at a time, retesting Safari after replacing each file. Delete any files causing the problem. You can replace files by right-clicking them in the Trash and selecting the "Put Back" option.