Beniben I didn’t have time to set it up currently so sorry for my question as I can’t look it up myself.
You may wish to find time, if you plan to launch using this method.
Each 'blog' belongs to a user, each post can reside in a tag (category) so with the right setup you can have what appears to be a multi-blog setup https://brickzip.com is a site I'm aware of that makes heavy use of the blog extension so might be worth taking a look at that site
(i'm not affiliated I just noticed it in a link in a post a week or so ago and thought it was quite well put together)
Find some time, setup a temp site and play around and of course ask lots and lots of questions