And to your second question, there is a pattern to how Bible translators use "saint" and "holy one". Traditionally, English translators tend to used "saint" rather than "holy one" in the New Testament and the Psalms and "holy one" rather than "saint" in the Old Testament and when referring to angels, Jesus, or God.
I believe that the tradition goes back to at least to the main English Protestant Bible, the King James Version (KJV), which was first published in A.D. 1611.
There are 36 occurrences of the word "saint" (or "saints") in the KJV Old Testament, compared to 62 occurrences of it in the New Testament. Of those in the Old Testament, 21 of them occur in the book of Psalms, which was sung by the congregation in Church of England services. This is significant because congregations would sing the Psalms in reference to themselves, identifying with the people spoken of in the Psalms and making these prayers their own, applying these passages to themselves directly, as with the New Testament (the rest of the Old Testament being "Old Covenant" and thus only indirectly applicable to New Testament believers).
That means that, when the modern Christians were expected to directly apply a passage of Scripture to themselves-either in the New Testament, because it governs the Christian age, or in the Psalms, because Christians prayed these in church-the overwhelming preference was for the term "saint," with a total of 83 occurrences (the New Testament plus Psalms), compared to only 15 when the audience was not expected to directly apply the Scripture to themselves (the rest of the Old Testament).
The mirror image of this occurred with the term "holy one" (or "holy ones"). This occurred 46 times in the KJV Old Testament compared to only six in the New Testament. Of the Old Testament occurrences, only six were in the book of Psalms, and every one of those was a reference to God or the Messiah, except for one reference to David. Of the six occurrences in the New Testament, five were references to Jesus and one was a reference to God.
The term "holy one" was thus never used when the audience was expected to apply it directly to themselves; "saint" was always used instead.
The rule was thus: If the audience is expected to apply the passage to themselves, use "saint," otherwise use "holy one," and if it is a reference to God or Christ be especially sure to always use "Holy One" instead of "Saint."
This tradition is still present in modern Protestant Bible versions. The Revised Standard Version and the New International Version have very similar term counts.