Partial iCloud Sync

Hi. I am just wanting to check that want I want to achieve with iCloud sync will work in the way I expect

Currently I have a Late 2014 1TB mac mini with iCloud Drive synced, but not Desktop/Documents. I have circa 350GB of home videos that I have stored on the Mac Mini and backed up to local external HDDs (including an offsite one). I am thinking about upgrading to the 2TB iCloud storage so I also have an online back up of the videos.

However, I am going to be shortly buying a new MB Air and was thinking about only buying a 256GB version.

While I know I can select the optimisation option I am worried about the storage being fully used on the MB Air. Therefore I am l looking at options to be able to backup the videos without them going on all other devices (accepting that I then wont be able to access them on those other devices)

What I was thinking was to turn on the sync for Desktop/Documents on my Mac Mini and ensure the videos are included in this. Then on the new Air only turn on iCloud Drive sync, but not Desktop/Documents

If I have understood correctly, this will mean the video on the MM will sync into the Cloud, but the Air wouldn't then download them. Is that correct?