an emphatic "now": what is in fact the case at present, set over against what was before or what was only supposed
This is the emphatic "now." Greek already had a plain, everyday word for the present (νῦν); this is the stronger form of it, used only twenty times in the New Testament, and eighteen of those times it comes paired with a small connecting word so that it lands as "but now" at the front of a sentence, like a hinge.
Its range holds together because of that hinge. Whether the writer is contrasting two moments in time, two conditions of a person, or a supposition against the truth, the word does the same job: it turns away from something set aside and points to what is actually the case. When Paul says God's righteousness has "now" been revealed apart from the law, and when he says that "as it is," God arranged the parts of the body just as he wished, the shape of the sentence is the same. Only the thing being set aside changes.
That is why English has to shift its wording. Where what is set aside is a former time, "but now" carries it well. Where what is set aside is a supposition the writer has just raised for the sake of argument, "now" sounds odd in English and translators reach for "but as it is" or "but in fact." The Greek has not changed; the thing it is turning away from has.