I have heard muslims claiming that quran has been perfectly preserved, letter for letter, word for word, dot for dot but I have heard some counter claims as well and have seen a YouTube video by a Christian missionary who purports that are around 31 different qurans. I am not sure if the claims by the Christian missionary are truthful or not.
Muslims also try to defend their claims stating that quran was revealed in 7 different styles or ahrufs. Also, as per my knowledge muslims don't have the original quran compiled by uthman. There is also no complete quran available since then and the various quranic fragments such as the sana manuscript and the Birmingham quran that contain variances from the quran of today also add to the confusion.
So my question is really simple. I'd like to know if there are any unbiased academic scholars who believe in the perfect preservation of the quran. I would like to start by reading some of their books or opinions because it would help me in clarifying some of my doubts on this topic.