Hi @mjkang thanks for posting in the community! That's a great question the differences between the account types are the features that are available to each. For a comparison of each account time I recommend taking a look at our Lucidchart Plans article. 

Regarding your question about commercial use Lucid is supportive of the use of our software in your materials.

If you created the document you would like to use yourself then you are the owner of the diagram and can use it however you would like. Others who have used diagrams in books or publications have cited the diagram image with "Created in Lucid (lucid.co)". We encourage you to do this as well but it is not required as you own the work you created in Lucidchart.

If you would like to use a template we created you may reference us with the following citation: Created in Lucid (lucid.co)

We also ask that you reference/cite any product screenshots as “Lucid lucid.co” or other wording that references both our full brand name and our website.

I hope this helps! Please feel free to let me know if you have any further questions.