The difference seems to be conveyed best by saying that the Reformed Christian thinks theologically, the Lutheran anthropologically. The Reformed person is not content with an exclusively historical stance but raises his sights to the idea, the eternal decree of God. By contrast, the Lutheran takes his position in the midst of the history of redemption and feels no need to enter more deeply into the counsel of God. For the Reformed, therefore, election is the heart of the church; for Lutherans, justification is the article by which the church stands or falls. Among the former the primary question is: How is the glory of God advanced? Among the latter it is: How does a human get saved? The struggle of the former is above all paganism- idolatry; that of the latter against Judaism- works righteousness. The Reformed person does not rest until he has traced all things retrospectively to the divine decree, tracking down the “wherefore” of things, and has prospectively made all things subservient to the glory of God; the Lutheran is content with the “that” and enjoys the salvation in which he is, by faith, a participant. From this difference in principle, the dogmatic controversies between them (with respect to the image of God, original sin, the person of Christ, the order of salvation, the sacraments, church government, ethics, etc.) can be easily explained.
Reformed Dogmatics — Vol. 1: Prolegomena (Baker, 2003), 177.
This quote reveals how R2K is more Lutheran that it is Reformed. R2K is not concerned with how God’s glory is advanced in the common realm because God’s glory can’t be advanced in the common realm because the common realm is common. It is a realm where good and evil grow together and the only realm where the glory of God that is advanced happens in the Church. If R2K struggles against paganism / idolatry it struggles against it only in the Church. It is clear, per Bavinck, that R2K’s primary struggle is Lutheran in as much as it see’s works righteousness everywhere, especially in those of us who are not R2K. R2K does not think it is possible to make anything in the common realm uniquely subservient to God.
R2K is not Reformed. It is instead a mish mash of Lutheran thinking, and Anabaptist thinking, heavily seasoned with Dualism.