There is a long thread which discussed the pros and cons of self-hosting, vps and other options in comparison to Moodlecloud, but the difference is massive, both in limitations and responsibilities. MoodleCloud Starter only provides the "custom certificate" extra plugin and does not allow installation of custom themes or plugins (which is possible when self-hosting).
You can view the list of extra plugins on https://moodlecloud.com/app/en/, by clicking on the "+" sign right of "Extra plugin pack". A list with more detailed descriptions is available on https://moodle.org/plugins/browse.php?list=set&id=80 - note that most of them are only available on "school plans" (which are available to anyone, don't let the name confuse you).
Since MoodleCloud offers a free tier from which you can later upgrade, I would suggest you get started with it. You can later export your courses and import them into your self-hosted site if you wish.
Hopefully this helps make sense of it.