It's interesting that both Paul and James are the only ones that use this word "doer(s)" in regard to the Christian, Where Paul obviously applies it to 'the law", James applies it to "the word" (James1:22, 23, 25) and then to "law" in James4:13.
When James applies it to "the word", in context he attaches this to 'the perfect law of freedom" in James1:25 and in that same verse
defines "a work doer" as one who looks and remains intellectually with focus into "law" which is emphasized by word placement, then elaborated as "the perfect law of freedom". Then he adds that this person does not become a forgetful hearer, "but a doer of work" (again, doer looks to be emphasized). It is these who will be blessed in their "doing."
In the context, of James1, this "word", "this perfect law of freedom" is the "word of truth" God used to birth us as a kind of first fruits of His creatures (James1:18) (the new man in Christ). The word and the perfect law of freedom is the Gospel. So, the Gospel is Law and belief in Jesus Christ is commanded (1John3:23, et.al.).
I guess the task is to go back to Paul and figure out which Law he's speaking of and
in what context, especially since he says "God will render to each man according to his works" and then he says eternal life will be given to those who in endurance of good work are seeking glory and honor and incorruptibility/immortality, and before he speak of law doers. And especially since Paul is speaking in the context of judgment "in the day when God will judge the secrets of men by Jesus Christ, according to my (Paul's) Gospel" (Rom2:16). There's that "Gospel" again, which James correlates to the Perfect Law of Freedom".
FWIW, I'm not Roman Catholic, and I was taught by Protestantism, that RC was evil with its "works salvation". And I agree that works need to be understood well. But IMO this position within Protestantism has a range of explanation and it has come to be a far swung pendulum in reaction to RC. Some of this reaction has trended into absurdity and "work" has become a proverbial 4-letter word. Unless I miss my guess,
@RandyPNW has come to some of this conclusion as well and I can see in his posts where he is deriving some of his comments about work from Scripture.
As an aside but pertinent, do any of us think we're going to be judged by Mosaic Law that was fulfilled by Jesus Christ and is not valid for the righteous as their rule of life?