Is there any difference between talking blather and talking nonsense? If there is, what is this? Which one is best choice for the above case and why? And what can be the another usage of rest choice?
Another query is- are first and third sentence same?
Literally, "talking blather" and "talking nonsense" have the same meaning. Subjectively, I feel that "blather" is more foolish and playful but "nonsense" is more serious. However, it is more usual to say "blathering" rather than "talking blather", since "blather" is also a verb. "Blather" is also more pejorative, it implies that the speaker has a negative opinion about what is being said.
The first and third sentences are different. In the first sentence, I meet people and those people talk nonsense. In the third sentence, the people that I meet are talking nonsense when I meet them. The first sentence describes who they are, the third sentence describes what they are doing when I meet them.
