Rev 21:1 And I saw a new heaven and a new earth: for the first heaven and the first earth were passed away; and there was no more sea.
Rev 21:2 And I John saw the holy city, new Jerusalem, coming down from God out of heaven, prepared as a bride adorned for her husband.
Rev 21:3 And I heard a great voice out of heaven saying, Behold, the tabernacle of God is with men, and he will dwell with them, and they shall be his people, and God himself shall be with them, and be their God.
At time NJ is here, Father will also live on Earth, in NJ.
However, though the thousand years and little season afterwards, the Father is still in heaven:
Rev 20:7 And when the thousand years are expired, Satan shall be loosed out of his prison,
Rev 20:8 And shall go out to deceive the nations which are in the four quarters of the earth, Gog and Magog, to gather them together to battle: the number of whom is as the sand of the sea.
Rev 20:9 And they went up on the breadth of the earth, and compassed the camp of the saints about, and the beloved city: and fire came down from God out of heaven, and devoured them.
This proves neither the NHNE nor NJ exist prior or during the thousand years and only happen after the GWTJ...so yes, Rev 21 comes after Rev 20 chronologically.
A second proof is there is no sea when NHNE happens yet at the GWTJ the sea still exists:
Rev 20:13 And the sea gave up the dead which were in it; and death and hell delivered up the dead which were in them: and they were judged every man according to their works.
Rev 21:1 And I saw a new heaven and a new earth: for the first heaven and the first earth were passed away; and there was no more sea.