1)
What is "Es Tuv Eretz Mitzrayim"?
1.
Rashi #1: It is Eretz Goshen.
2.
Rashi #2: Pharaoh unknowingly prophesied 1 that when Yisrael were redeemed from Egypt, they would take all the wealth of Egypt with them, leaving it [empty] like the depths of the sea - where there are no fish. 2
3.
Ha'amek Davar: I will appoint you to work for me in the best part of Egypt.
2)
Why does it say "u'Vo'u Elai"?
1.
Malbim: Yosef has authority to tell his brothers to come to him, but not to come to Egypt to settle; refer to 45:19:1:5.
2.
Ha'amek Davar: You will remain in Egypt under my jurisdiction and service.