Just a few observations. Tyndale translated his English version of 1525 from the 1522 edition of the Greek text of Erasmus.
The KJV was to be a revision of the Bishop's Bible, the last bible to be "authorized" (1568) by both the Crown and the General Synod of the Church of England. The Bishop's bible was prompted by the popularity of the Geneva Bible of 1560. In 1563 the Archbishop of Canterbury, Matthew Parker, initiated a revision of the Great Bible (Miles Coverdale), which was the earlier bible to have been "authorized" by both the Crown and the General Synod. The Bishop's Bible had a distinct "Episcopalian" flavor in its polity as opposed to the "Puritan" flavor of the Geneva bible. It was "authorized" by the General Synod of the English Church Convocation in 1571. The Bishop's bible reflects a lack of harmony between the different groups of translators and never gained much popularity with the laity in spite of being "authorized" by Crown and General Synod. It has sometimes been referred to as the 4th revision of Tyndale's bible.
The supposed "Latin Corruptions" which can be found in all three of the above English versions can be traced back to Erasmus. Erasmus had 5 Greek manuscripts available for his personal use in 1516 when he published his first edition of the Greek New Testament. 1, an 11th century manuscript of the Gospels, Acts, and the Epistles. 2, a 15th century manuscript containing only the Gospels. 2ap, a 12th century manuscript containing Acts and the Epistles. 4ap, a 15th century manuscript containing Acts and the Epistles. And 1r, a 12th century manuscript containing most of the Revelation.
Erasmus had access to the readings of Codex Vaticanus which was in the Vatican library. In fact he divided his small number of manuscripts into two groups, those that agreed with Vaticanus and those that did not. (See Kenyon, Our Bible and the Ancient Manuscripts.) Erasmus rejected the text of manuscript 1 because of its similarity to Vaticanus. Erasmus used primarily 2 and 2ap because he knew them to be the best representatives of the Byzantine textform.
However, there will always be some parts of any manuscript that are either missing or illegible, and when he could not reconstruct a Greek reading he often resorted to his Latin Vulgate and back-translated that reading into his Greek New Testament. This can be seen in Matthew 10:8; 27:35; John 3:25; Acts 8:37; 9:5-6; 20:28; Romans 16:25-27, and, of course, the Johannine Comma, and the last 6 verses of Revelation.
However, each of those "Vulgate" readings have subsequently been found in the Greek manuscript textucopia (with the exception of the last 6 verses of Revelation and even then Hoskier believes Codex 141 may reflect that reading). The manuscript evidence in support of those "supplied" readings is always in the vast minority, but evidence has been found to support those readings.
As to the claim that the NIV is based on "dozens of Greek texts" which antedate the manuscripts used by Erasmus, that is correct. But subsequent to the time of Erasmus thousands upon thousands of Greek manuscripts have been discovered that not only follow the Byzantine readings of 2 and 2ap and date to as early as Aleph and B, and often those readings can be found in manuscripts that predate either of the primary Alexandrian uncials.
And, in fact, the latest edition of the Critical Greek New Testament (UBS 4) has far more Byzantine readings than its earlier counterparts UBS 1, 2, and 3.
The controversy regarding which textform is superior, and which bibles translated from those textforms are superior, is a controversy that will not be soon settled. My advice is find a bible that you believe is as true to the intent of the original writers as possible and live by every word in that bible. I would rather have a person live by a sub-standard bible than to champion the best bible available in English but not live according to its precepts.
