Hey Robert,
EasyBlog 5 settings is a little more advanced than EasyBlog 3.x. It respects 3 different settings (inherited)
1. It will look for your menu settings (If you have one, otherwise it will inherit from the next item)
2. It will look for your category settings (If your category settings are set to inherit from global, it will inherit from the next item).
3. It will look for your globla settings under Settings > Layout > Post Options.
In these settings you can find the option "Post author box" and you can just switch them off