Both the KJV and the NKJV use the TR primarily. But occasionally they depart from it. Sometimes they KJV sticks with it and the NKJV goes with the NU and/or W&H --and sometimes the KJV just follows its own path.
Here are a few examples.
Col.3:17b
WH NU : giving thanks to God the Father (NKJ)
Var/TR : giving thanks to God and the Father (KJV)
Philippians 2:15a
TR WH NU : that you may become blameless (NKJ)
Var : that you may be blameless (KJV)
Eph. 2:5a
TR WH NU : dead in trespasses (NKJV)
Variant 2 : dead in sins (KJV)
1 Peter 5:13
TR WH NU : She who is in Babylon (NKJV)
Var 1 : The church that is at Babylon (KJV)
Jude 3
WH NU : our common salvation (NKJV)
Var 2/TR : the common salvation (KJV)
Jude 19
WH NU : These are [the ones]who cause divisions (NKJV)
Var/TR : They who who separate themselves (KJV)
Here are a few examples.
Col.3:17b
WH NU : giving thanks to God the Father (NKJ)
Var/TR : giving thanks to God and the Father (KJV)
Philippians 2:15a
TR WH NU : that you may become blameless (NKJ)
Var : that you may be blameless (KJV)
Eph. 2:5a
TR WH NU : dead in trespasses (NKJV)
Variant 2 : dead in sins (KJV)
1 Peter 5:13
TR WH NU : She who is in Babylon (NKJV)
Var 1 : The church that is at Babylon (KJV)
Jude 3
WH NU : our common salvation (NKJV)
Var 2/TR : the common salvation (KJV)
Jude 19
WH NU : These are [the ones]who cause divisions (NKJV)
Var/TR : They who who separate themselves (KJV)