The lines you have indicated present Adam as possessing a child-like innocence, joy and pleasure that is completely absent from Satan and the way that he is so envious and bitterly jealous of the lack of power and stature that he has compared to God. Note the response of Adam when he wakes into his life and how he responds to the beauty of his surroundings:
about me round I saw
Hill, Dale, and shadie Woods, and sunnie Plaines,
And liquid Lapse of murmuring Streams; by these,
Creatures that livd, and movd, and walk'd, or flew,
Birds on the branches warbling; all things smil'd,
With fragrance and with joy my heart oreflow'd.
The use of alliteration in "liquid Lapse" and onomatopoeia in "murmering Streams" all serve to create a happy, tranquil tone as Adam marvels at the world he has been placed in. His response is to see everything as "smiling" and then his emotional reaction is that his "heart overflow'd." Adam has a simplicity and a real appreciation of the beauty of nature. Satan is a character who, throughout the poem, displays an inability to enjoy the simple pleasures of life as he is so consumed with his power-hungry desires.