Flashing the same ROM over will preserve your data.
Generally speaking this is called “dirty” flash and as long as the content of your Data partition is compatible with the ROM image you apply there will be no lost.
Often, flashing a ROM image from the same provider with the same Android version is OK.
For example, dirty-flashing 0.16Q /e/ over 0.15Q /e/ is okay.
Sometimes, you can also upgrade Android without data loss, for example flashing 0.16R /e/ over 0.15Q /e/, but sometimes it may fail because Data content incompatibilities.
I’m not aware of OnePlus devices, but for all this devices I know you can open the zip ROM file and check the flashing script inside 
Often, it will just overwrite the System and Vendor partitions.
That being said, I must apologize (again!) : deleting the Settings apk may not force a re-install. I’ll have to check further.
However you can still apply the procedure from my previous post, I tested it this morning and it worked fine (although it may not achieve what was expected ).
It is OK, but the path may appear differently from TWRP.
You problem here is not having root access. If you had, we could uninstall the Settings app and re-install it from the apk …