Learn Romanian: Priveliștea este nespus de frumoasă din acest balcon. - The view is unspeakably beautiful from this balcony.

No, it remains invariable. When used in the superlative locution nespus de (unspeakably or incredibly), nespus acts as an adverb modifying the adjective, so it never changes form. Only the main adjective, frumoasă, agrees with the feminine singular noun priveliștea.

Could I replace nespus de with one of the other superlative phrases from this lesson, like din cale afară de?

Absolutely! You could say Priveliștea este din cale afară de frumoasă (The view is extraordinarily beautiful) or Priveliștea este extrem de frumoasă (The view is extremely beautiful). They all function exactly the same way, always requiring the preposition de right before the adjective.

What is the literal breakdown of the word nespus?

It is formed from the past participle of a spune (to say or tell), which is spus, plus the negative prefix ne-. Literally, it means "unsaid" or "untold." Paired with de, it creates the absolute superlative meaning "unspeakably" or "beyond words."

Why is it din acest balcon (from this balcony) instead of de pe acest balcon (from on this balcony)?