Currently the ability to have cells automatically resize to better fit long or short lines of text is not built into the product. The Tableau website has an Ideas section where customers can add, comment, and vote on features they would like to see in the product. Votes are used to help prioritize new features. Our Development team also loves to see everyone's use cases in the comments, which helps them better design features that will meet the most possible needs.
I recommend voting/commenting on Automatic resize cell to accommodate wrapped lines and Row height should have "can grow" feature
Hope this helps!