Apple's implementation of samba is truly pants and you're arguably better with NFS (doesn't play nice for TM or various Apple libraries) or AFP (until Apple EOL client AFP).
But splitting up the current share into directories with fewer files, i typically stick to a few thousand, massively helps.
Other options you can try within MacOS is to
enable DSDontWriteNetworkStores to stop creation and reading of .DS_Store files (sounds like you've already done this); confirm client-side packet signing is disabled (should be on 13.4+) otherwise
disable it; disable Finder's icon previews by pressing CMD + J in your directory, uncheck
Show icon preview (click
Use as Defaults if you want to make it global).
I've never really delved into Unraid but see if you can enable the samba
vfs_fruit module which attempts to improve compatibility with MacOS (it can help but it can also cause other headaches, especially in mix platform environments), otherwise see if you can enable AFP (or Netatalk) or NFS for your shares and give that a whirl.
Edit - Quick Google found these that might be worth a read,
Unraid and vfs_fruit and a
Netatalk plugin.