The fact the Apple Mail function but only in Safe Mode indicates there is no need to remove the plist files nor are they possibly corrupted.
Safe Mode does several things including Only Load Apple Software, extensions and fonts. It also eliminates Third Party Software, extensions and Fonts from loading.
Immediately glean, there is something not right in the User Account Or some Third Party software is interfering with the normal operation of the OS.
There are two route to isolate where this issue is. One is create a new User account for testing purposed only and test if the issue is presented when booting in Normal Mode. If not presented - the issue is in the original user account.
The second route is Suggest downloading the Application Etrecheck https://etrecheck.com directly from a well respected ASC Contributor.
The application is free or paid from added features.
Run the application with Full Disc Access ( Security & Privacy - Full Disc Access ).
It will take a Snap Shot - both the hardware and software.
The Report will Not Reveal Any Personal Information.
Post back the Full Report - copy and paste - using the Additional Text Icon ( 3rd Icon to last )
We can have a look at the report for possible issues and may have possible suggestions to resolve the issues.
Any Third Party Applications that will interfere with the normal operation of the OS, alter, modify, remove or delete or attempt to do so is an invitation for disaster and may require a Reinstallation of the OS.
This includes AntiVirus, Cleaners, Optimizes, UnInstaller etc.
