How to stop long downloads/uploads to iCloud when browsing with Finder shared folder in other macs on the same LAN
For simplicity, I recommend using SFTP to transfer files. SFTP moves files using an SSH session. SSH can do authentication by user credentials, or by public keys. 

It's secure, fast on modern hardware, and with modern tools, relatively convenient.

Here's one way to do that:


Turn on "Remote Login" in System Preferences->Sharing on the remote Mac (be sure to Allow access for: All users)
Create user credentials on the remote Mac
Download an FTP client that can do SFTP. My recommendation is Filezilla.


Use the FTP client to log in by SFTP to the remote Mac, and Bob's your uncle.