Thank you! I am a little bit confused. Do you mean the cloud is symbolic of loneliness? Again, Is it appropriate for me to use as free as a cloud?
I don't think clouds necessarily mean loneliness in English speaking cultures. That poet (Wordsworth) used that image and his poem is famous, but they can be thought of in many ways. Joni Mitchell has a famous song that begins
"Bows and flows angels hair and ice cream castles in the air, and feather canyons everywhere, I've thought of clouds that way. But now they only block the sun, they rain and snow on everyone, so many things I would have done but clouds got in my way. I've looked at clouds from both sides now ..."
So I think poetry can make use of whatever images the poet wants, either drawing on cultural references or creating new ones. When translating poetry there are different schools of thought, but the current fashion is for staying as literal as possible and letting the reader feel the culture and word game of the original. Saying "free as a cloud" has a clear meaning for me. I did not know about the Chinese mythology you mention, but something of it is revealed and communicated in that phrase that is new to me. A footnote explaining its traditional roots in Chinese culture would deepen that perception, but it is not necessary for my understanding of the line.
BTW as others have said, be careful with tenses and articles (definite and indefinite) in English. Chinese does not use them, but English becomes confusing or odd to read without them.