iCloud sync of documents and desktop

As per this article https://support.apple.com/en-us/HT206985

You can organize and combine folders from multiple Macs when you turn on Desktop and Documents on those computers too. After you turn on Desktop and Documents on a second Mac, you'll find its files in folders with the same name as your second Mac inside your original Desktop and Documents folders. Then you can combine your files manually, but iCloud doesn’t automatically merge the files in case you want to keep them separate. Any edits you make are seamlessly updated in iCloud Drive. There’s no need to manage your folders and files again on your other devices .

If you have turned on iCloud Drive https://support.apple.com/en-in/HT204025 and desktops and documents box is checked , the data is saved on the iCloud Drive .

If you mean you are having two Macs , say Mac A and Mac B and you want the same Apple ID and password signed on both Mac so that iCloud data is similar on it , and what Mac contents do you want to differ , clarify it .

Once two Macs are signed in with same Apple ID and password on the same network , the existing documents on the primary Mac will get synced to the second Mac .

You can give a breakage in settings by opening system preferences > iCloud > the box of iCloud drive is to be checked , click on option button and uncheck the box of desktops and documents and click on turn off .

So , if you create new documents in the primary Mac they will be saved in the primary Mac itself and a pop up window will be shown , click on show in finder , these new documents will not be shown in second Mac , again to repeat the same concept what ever the data that was shared in two Macs will be constant and saved on the iCloud server .

But putting a barrier by unchecking the box of desktops and documents new data added in desktops and documents will get stopped .