| Quote #1 And we will all the pleasures prove, |
The speaker lists multiple country landscapes in quick succession to emphasize the variety of scenery and activities available in the countryside. And no matter where they go, if it's green, the two of them will be happy.
| Quote #2 By shallow rivers, to whose falls, |
Nature is literally and figuratively in harmony in the pastoral world. This is like one of those cheesy scenes from a Disney princess movie, when she prances through the forest and all the birds and trees sing with her.
| Quote #3 A gown made of the finest wool, |
Nature is not only in harmony with itself, it's willing and able to provide everything two people would need to survive. Of course, we're getting this through the speaker's eyes, so it's entirely possible that the picture we're getting of nature here is—shall we say?—less than accurate.