With regard to manuscripts of Mat. 19:16, no manuscript has 'good' in it twice. There is only one 'good' in verse 16. This is admitted to in one translation that puts 'good' in twice, in English:
"Good. All the texts omit. The accounts here (vss.16-27, Mark
10:17-26, and Luke 18:18-28) are partly identical and partly
complementary." The Companion ...
The King New James concerning The New Testment was based on the Textus Receptus, and it's for Matthew 19:16:
16 And, behold, one came and said unto him, Good Master, what good
thing shall I do, that I may have eternal life? (KJV)
Well, the greek equivalent is from Textus Receptus:
και ιδου εις προσελθων ειπεν αυτω διδασκαλε αγαθε τι αγαθον ποιησω ινα
The NKJV has this footnote for "Good[fn] Teacher":
NU-Text omits Good.
Similarly for "Why do you call Me good?[fn]":
NU-Text reads Why do you ask Me about what is good?.
It's all a matter of whether the translators favoured the NU-Text or the M-Text.
These variations from the traditional text generally represent the ...