Folders synchonization

I’m quite recent so please apologize if my question seems obvious or has been asked a thousand times
I would need some help/explanations or confirmations about nextcloud folders and synchronization .
I have already a Nextcloud folder
I would like to synchronize several other folders of my PC which are in different locations, for example:
I understood that if I want to have these folders synchronized in Nextcloud, I have to go to the synchronization client parameters, click on “add folder” and then select the folders that I want to store and synchronize in my nextcloud instance.
But then, directories will be copied to nextcloud folder, so I’ll have the content of these folders twice on my PC. Is it correct ?
So if I don’t want to have the files of the synchronized folders duplicated, I’ll have to move the folders I want to synchronize to the nextcloud directory ?
Thanks a lot

You can also uncheck the duplicates folders from syncing, so only one copy is held locally. This will just mean your folder structure will be different on other clients you sync with.

Another option to consider is moving it to the Nextcloud folder, and then you can replace the original path with a symlink.

Yes, replacing the original path by a symlink is indeed one solution.
Thanks a lot for your answer.