Yes, it is a good way to tell them apart. Adverbs do not change! Refer to this article (in Portuguese) if you want more examples of your definition (Congrats) http://www.recantodasletras.com.br/gramatica/1763249
How do we know when to use ser and when estar with the adjectives of size? This lesson has had ser with comprido and grande, and estar with largo and amplo. What's the difference? Is it depending on whether it belongs to a person? A camisa dela está comprida and a camisa é grande ? That would sort of make sense because in the latter it's describing an unchanging quality of the shirt but in the former it's saying how it fits on one person's body.