Those hidden files are created by macOS for various system functions. If you find them intrusive or unnecessary, you can try the tips mentioned below to prevent them from creating.
.fseventsd: This folder keeps track of changes to files and directories on the external drive. This helps applications that need the information. For instance, Time Machine needs it to make incremental backups.
To disable it on your external drive, try creating an empty .fseventsd folder and mark it immutable by running the following commands in Terminal:
/Volumes/Your_External_Drive_Name/
sudo rm -rf .fseventsd/
sudo mkdir .fseventsd
sudo chflags uchg .fseventsd
To reverse the action, try:
sudo chflags nouchg /Volumes/Your_External_Drive_Name/.fseventsd
.spotlight-v100: This directory contains the Spotlight index and related metadata for the volume. You can add this drive to the exclusion list of Spotlight to avoid it being indexed.
.TemporaryItems: This folder holds temporary files and folders created by different applications or system processes. They are safe to delete and are often managed by macOS automatically.
.Trashes: This is where files you delete from removable volumes are temporarily stored until you empty the Trash. To avoid its creation, always empty the Trash with your external drive connected.
._DS_Store: This file stores folder view settings for Finder. If you don't have view preferences on those drives, you can stop ._DS_Store from generating by running the command below in Terminal.
For USB drives:
defaults write com.apple.desktopservices DSDontWriteUSBStores -bool true
For network drives:
defaults write com.apple.desktopservices DSDontWriteNetworkStores -bool true
._filename: These AppleDouble files are created by macOS when you copy files to FAT32 or other non-Apple volumes and store resource fork data. Changing the format to HFS+ or APFS will stop them from creating.