The traditional interpretation of Romans 7:14ff argues that Paul's description of the spiritual impotence of the "wretched man" is the normative experience of all believers because of indwelling sin.
But this cannot be the case (our present struggles notwithstanding).
Compare 6:14, which we've been considering, to 7:14. In the former verse, the apostle tells us that those under the dominion of grace are not in bondage to sin. In the latter verse, however, he describes the experience of a person who is "carnal," and who is "sold as a slave to sin." To make matters worse, in 8:7 he categorically denies that the "carnal" mind, which is "hostile to God," can submit to God's law. But this is precisely what the "carnal" man does in 7:22 -- he "delights in the law of God in his inner being" (albeit without much practical success).
The answer to the question, "Is Romans 7 describing a regenerate or an unregenerate person?" must, therefore, be No.
Given the historical and covenantal interpretation of "under [the] law" offered in previous posts, we must conclude that the existential differences between the person described in Romans 7 and Romans 8 cannot be attributed to an existential experience, be it a Wesleyan "second blessing" or anything else.
Rather, the difference between the saint of chapter 7 and the saint of chapter 8 is redemptive-historical, as the text itself clearly states. The believer described in chapter 7 "serves" God, but does so "in the old way of the letter" rather than in the "new way of the Spirit" (7:6). In other words, the saint in Romans 7 is under the dominion of sin because he is under the dominion of the Mosaic law (cf. 6:14).
But as Romans 8 demonstrates, the New Covenant saint has died to the law and been "married to another." When Torah gave way to Pneuma on the day of Pentecost, impotence was eclipsed by power, bondage matured into sonship, and letter was swallowed by Spirit.