Can I set up an approval process on a blog?

Yes!

Read our guide here.

Can I make a blog post on another user's behalf?

No, whichever user profile is used to create the post will appear as the Author.

It is possible to log in as another user (provided you have their credentials and this is something your team will authorise) to make posts against their profile, however, this is not recommended.

The alternative is to use a Community Blog that allows different users to create posts, rather than just one person with an Individual Blog.