Respuesta :
"only landscapes" would turn to "videos that have only landscapes"
The answer to your question would be that the phrase that would replace the words "only landscapes" best to create a parallel structure is the following one: Videos that have only landscapes.
Parallel structure, also known as parallelism, is the repetition of a grammatical construction within a sentence. In this case, the repeated construction is the whole NP (the noun head and its modifiers: videos that have people in them/videos that have only landscapes).
