Increase Categories section

Categories (and the other taxonomy area if used) all have min-width: 150px, where excerpt has min-width: 250px

You can add the following to your theme css:

fieldset.frontier_post_fieldset_tax {min-width: 250px !important;}

if it is important that they have the exact same with, you can assign same width to both by:

fieldset.frontier_post_fieldset_tax {width: 250px !important;}
 fieldset.frontier_post_fieldset_excerpt {width: 250px !important;}

You can also increase the height using CSS:

fieldset.frontier_post_fieldset_tax {
width: 250px !important;
height: 400px !important;
}
fieldset.frontier_post_fieldset_excerpt {width: 250px !important;}

You can disable tags by unchecking “Edit Tags” in Frontier Post Capabilities settings.

So you are managing the capabilities externally.

Then you need to remove the capability: frontier_post_tags_edit

See here: http://wpfrontier.com/frontier-post-profiles-capabilities/