MacOS Sierra how to reduce priority of iCloud drive sync?
Bonus question, Exclusion: In MacOS Sierra, you have one option in Apple menu > System Preferences > iCloud > iCloud Drive Options > Desktop &amp; Documents Folders - on or off. It's all or nothing, therefore you should reconsider iCloud for small files, for example I tried it with some .dotfiles and very soon dropped that idea as my CPU time was eaten up. 

Same goes for Dropbox (but my experience is 1.5 year old here, so maybe Dropbox is now better-handling small files) Other thing I tried was syncing .zipped files / containers - that was working fine but in after a while I droped that too- what I found best is TimeMachine "set it and forget it" config you can access from the outside.

I know that it's not the answer you are looking for, I can only say from my experience, after few months of cloud syncing I put it on external solution where I sync a local drive and forget about it, QoS takes care of upload priority and file sync isn't my Mac's CPU problem.

Worth remembering: if you start using iCloud, there is no way to delete certain files (which is absurd) - for example you can't delete files Applications leave in your User ~/Library, I know it sounds crazy, but just google for "iCloud delete all preferences" or similar