Do I need an empty page for a different blog page?

So question is, do you really need to create an empty page just to set that page as the posts page/blog page?

Yes, you do.

If you use a static front page, and want to have a page for (blog) posts, then you need to create a separate static page, and assign it as “page for posts” in Settings -> Reading.

But now I have an empty page inside the pages overview, and I don’t really want that page. Clients try to put stuff in there and email me that it doesn’t show up and stuff like that.

Note that WordPress is addressing some of your UI concerns.