If you do it via the browser, then it's fine
Also no need to add the \ there in that case, it will handle everything for you. You'll see the \ will be added in the editor configs later on. I was checking against that, but since it crashes on startup, you don't get that far. My apologies for the confusion.
And no, the Divine Ascension DLC is not needed. It doesn't make a difference.
Also, when reinstalling, after uninstalling through steam, it is best to delete the folder manually from Steam\steamapps\common. It often happens that Steam leaves files in that it thinks are not part of the installation, and that messes with any subsequent installation.
You setup at least looks fine. So let's look in the files to see if everything was installed correctly. Could you check for me if "C:/Program Files (x86)/Steam/steamapps/common/Divinity Original Sin 2/Data/Public/Game/Assets/Materials/Editor/Gizmo_Lines.lsb" actually exists in your file system?
Sincerely,
Kevin
