I can’t claim to be an expert on the subject but I have seen a few debates between Ehrman and Daniel B Wallace and what scares me about Ehrman about is he is very similar to the Watchtower, dealing more in conspiracies than probabilities
All Christian scholars know there are a number of textural variations. Scribes aren’t photocopy machines. There are even about 20 verses that might have been just plain added. Doctrinally it doesn’t change anything. It is the 99.5 % that is the same that is more interesting than the .5 that is different.
Since we don’t have the original copies of the new testament , how do you know it wasn’t all changed ? Well that kind of logic seems to be the foundation of all so called Christian cults, the bible is the inspired word of god, expect where it was changed. If the 5000 or so 3rd century copies that are 99 % the same isn’t enough proof that it most likely wasn’t altered , nothing will ever be enough proof.