Those four articles by Justin have been the standard Acts 9 understanding of that issue for some sixty years or more (though it also appears that Darby had held to that much over more than a century ago).
Which is, and is based on the understanding that Paul preached the truth of Ephesians two throughout his Acts ministry, and not at some later point, as is for example, the different understanding on this by others within Mid-Acts (those STP was referring to as the 3% who hold his and heir's "later in Acts" understanding on this).
Those four articles - the one you posted the link to, Musterion, and Justin's additional three:
The old and new covenant are both made to Israel, but in the new covenant God performs where they could not.
It makes perfect sense, then, that the apostle of grace would be an able minister of the new covenant, since grace is what sets the new covenant apart from the old, and it is grace which sets the mystery apart from everything (Israel, the law, the covenants – 2 Cor 5:17).
More is written about here and here, and here...
...are basically the standard view...of the same Spirit, different application, or the principle I keep going on about.
Though Justin did not appear to address the actual sense of Paul's "of the spirit" (lower case "s") but appeared instead, to attribute that as referring to the Spirit (capital "S").
Which is odd, if I am correct on that, as he is KJVO.
Paul is actually referring to a principle the Lord had also referred to...
John 6:63 It is the spirit that quickeneth; the flesh profiteth nothing: the words that I speak unto you, they are spirit, and they are life.
The Lord was relating there that He was ministering through His Words, to the spirit of men. That just as it is the spirit of a man that gives his flesh, his body its life, His words were able to give a man's spirit the life of God.
John 1:12 But as many as received him, to them gave he power to become the sons of God, even to them that believe on his name: 1:13 Which were born, not of blood, nor of the will of the flesh, nor of the will of man, but of God.
In Paul's application of that, the source and its' principle are one and the same Spirit based principle, at the same time that its application differs within the Israel of God in contrast to its application within the Body of Christ.
Being that he is dealing with the Corinthians in their focus on their own flesh, Paul is referring to Romans 7 and 8 issues, there in 2 Cor. 3:6's "not of the letter, but of the spirit: for the letter killeth, but the spirit givet life."
Thus his relating there...
2 Corinthians 3:5 Not that we are sufficient of ourselves to think any thing as of ourselves; but our sufficiency is of God;
Or what the Spirit of God was now enabling in the spirit of men through Paul's unique gospel.
In contrast, Paul basically reminds the Corinthians there in 2 Cor. 3; that the Law had only been able to minister through the flesh, and as a result, was weak; in that it was weak through the flesh, and as a result, had not been able to bring about in man that righteousness of the Law it had promised to give that man who could meet its required "patient continuance in well doing" Rom. 2:7.
Thus, the Spirit did not only free the Grace Believer from those strictly by the letter of the Law ordinances under the Law that had been so contrary to man; so against him; but was now empowering them by the same Spirit "without the Law" Rom. 3:21.
Galatians 3:1 O foolish Galatians, who hath bewitched you, that ye should not obey the truth, before whose eyes Jesus Christ hath been evidently set forth, crucified among you? 3:2 This only would I learn of you, Received ye the Spirit by the works of the law, or by the hearing of faith? 3:3 Are ye so foolish? having begun in the Spirit, are ye now made perfect by the flesh?
Galatians 4:3 Even so we, when we were children, were in bondage under the elements of the world: 4:4 But when the fulness of the time was come, God sent forth his Son, made of a woman, made under the law, 4:5 To redeem them that were under the law, that we might receive the adoption of sons. 4:6 And because ye are sons, God hath sent forth the Spirit of his Son into your hearts, crying, Abba, Father. 4:7 Wherefore thou art no more a servant, but a son; and if a son, then an heir of God through Christ. 4:8 Howbeit then, when ye knew not God, ye did service unto them which by nature are no gods. 4:9 But now, after that ye have known God, or rather are known of God, how turn ye again to the weak and beggarly elements, whereunto ye desire again to be in bondage?
That right there is Romans 1-8 and Ephesians 1-6 truth, by the way.
Galatians 5:2 Behold, I Paul say unto you, that if ye be circumcised, Christ shall profit you nothing. 5:3 For I testify again to every man that is circumcised, that he is a debtor to do the whole law. 5:4 Christ is become of no effect unto you, whosoever of you are justified by the law; ye are fallen from grace. 5:5 For we through the Spirit wait for the hope of righteousness by faith.
There's a whole lotta sufficiency going on there in all that in the spirit of men by and through the Spirit of God!