Lol - you might, or might not...care for my answer.
Paul is basically relating that he always has the Lord in mind in his dealings with others; that he is ever aware that one day; how he had conducted himself with others during his dealings with them will be called to account.
The key is the phrase "we are made manifest unto God."
It is a common theme in his writings.
Often, he uses the phrase "in the sight of God."
This is all tied, not to the Believer's inheritance, but to the reward of said inheritance and is the issue of how fit for service in glory (in said inheritance) one will be found one day, that how we conducted ourselves in our body now, will have prepared us for, then.
Some will be found fit for not much beyond sweeping floors and others will be Generals and all the other levels of service in glory...in between.
This is an entire study on what life in glory will be like.
There is much more to salvation than all this endless back and forth about who is right, who is wrong, who is up to no good, and all the rest.
There is the bigger issue of why God is even saving men to begin with, and how our conduct now impacts our rewards as to service then.
This life is merely a dress rehearsal for our life then
In this, the terror that Paul is talking about is his concern that he not be found to have disappointed the Lord; Who had wanted the best for and in each saint.
It is what He saved us unto to begin with - the purpose of salvation.
These greater issues were ever in Paul's mind; both in his teaching, and in his own conduct.
There are the various and glorious eternal issues far beyond all this mere baby talk that too many never seem to get beyond and the Corinthians were a prime example of Believers ever at one another's throats as to who was better, more accepted, who had started what nonsense first, and so on.
Both of his Epistles to them are fascinating as to these kinds of issues, their solutions, eternal consequences, and so on.
Study out the various passages in Paul's writings where he talks about being "presented unto the Lord" one day, and also, those passages where he uses the phrase "in the sight of God."
As to your question about what I would have said had James written the above passage by Paul - again you are showing you do not know where each of those men were coming from.
They were not dealing with similar issues in the same way.
Acts 21:18 And the day following Paul went in with us unto James; and all the elders were present. 21:19 And when he had saluted them, he declared particularly what things God had wrought among the Gentiles by his ministry. 21:20 And when they heard it, they glorified the Lord, and said unto him, Thou seest, brother, how many thousands of Jews there are which believe; and they are all zealous of the law:
21:25 As touching the Gentiles which believe, we have written and concluded that they observe no such thing, save only that they keep themselves from things offered to idols, and from blood, and from strangled, and from fornication.
Anyway, hope that keeps you busy studying out life in glory one day
Perhaps along the way, you'll finally put away this works for and or in order to maintain salvation confusion of yours.