If you add a link via kirbytext, you can give it a class:
(link: http://wikipedia.com class: inline-link)
Then you can style it via your stylesheet.
Your home buttons would get another class, maybe
nav-link or whatever (but I don’t know why you add them via your text field and not via a tag in your template).
As regard the image caption, you add it as a separate paragraph. I wouldn’t do that but add it as a caption to the image ( where it belongs semantically) within the image tag
(image: someimage.jpg caption: My caption class:someclass)
Then you can either style all image captions in the same way, or you add a class like in the example.
To get a better understand of Kirbytags and their options, you might want to have a look at the docs: https://getkirby.com/docs/content/text