The first question: Pay attention to the implied meaning of the expression "China's poems", that is, "China's poems", that is, compare China's poems as a whole with those other than "China". Then, the premise of comparison is to ask this question (the overall impression of China's poetry? ) One must have a certain understanding of China's poems and foreign poems. Only when he knows a certain number of Chinese and foreign poems at the same time can he have a comparative idea. I wonder if a reader who is only proficient in China's poems (such as Tang poetry) or Shakespeare (China people or foreigners) does not have the concept of "Chinese and foreign" in his mind, and naturally there will be no doubt about "the overall impression of China's poems".
The second question is precisely because Welland lived in a late era, and later generations are always summative. Most importantly, western literary theory is considered to be the most advanced and scientific literary theory in Qian Zhongshu's era (especially after the New Culture Movement). Qian Zhongshu personally studied western literary theory in Europe, so he came to his conclusion.
I hope I can help you. Thank you for reading.