Qual è la differenza tra Happy is the one ~ e The one ~ is happy ?Sentiti libero di rispondere con un esempio.

I may be wrong, but I think it’s (happy is the one-)passive voice versus active voice(the one-is happy).
Active voice is when the subject is put before the word that the verb is being applied to.
Passive voice is when the word that the verb is being applied to is put before the subject.
Active voice example: The one who loves is happy. She delivered the mail.
Passive voice example: Happy is the one who loves. The mail was delivered by her.
Active voice is more suitable in essays and professional writing, while passive voice is more suited for free, poetic writing.