I have put some effort to get Kobo Sync working with Calibre-Web. My experience I have made led to a
german tutorial I have written for the setup.
My conclusion is: Calibre-Web is a good choice to sync books wirelessly. But it is not the right choice if you want to sync hundreds of books - this will lead to sync errors. I don't sync more than 60 books with CW.
What's also nice: the sync of the reading-status. I have 4 Kobo Readers and that's a welcome feature for more comfort handling multiple readers.