Pre 1611 Bibles (Tyndale, Coverdale, Matthew, Great, Geneva, Bishops') are all pure Bibles. They do contain impurities in the same way that the 1611 Edition contained impurities, and they also contain impurities in text and translation. But this does not mean that they were not pure, nor the Word of God.

Remember that Psalm 119:140 says "very pure" which means there is degrees of purity. So Tyndale was pure. But in time, there was a purer Bible: the King James.

Also, Psalm 12 specifically speaks of how God's words are tried and undergo a process to ensure that they are pure. This happened in English. God's words in Tyndale's Bible are better presented in the King James Bible. (Tyndale's work was incomplete anyway.)

We know that some words in Hebrew were hard to know the meaning, but this was resolved by doing the best possible in the KJB translation, and their choices have been afterward vindicated. It is really a modernist opinion to come against the KJB, though there were others who for evil/wrong reasons came against the KJB such as Broughton, Romanists and even some Puritans in the Commonwealth.