It seems that, going by what we read in the Gospels that only Luke should be assumed to have been writen by luke ( and acts too of course).
Paul is tricky because Paul wrote by his own hand (and admits as much at times) and dicted to others (and admits as much at times).
The issue is HOW much was ALL PAUL and how much was what the person writing thought Paul meant or how much the person writing to finish a letter that Paul never finished, added.
That is why it is crucial to take the WHOLE of Paul and to judge the authenticity of the controversial PARTS of disputed letters with th ose recognized as being directly from Paul.
That is why the NT is NOT ONE stand alone document but a collection of works of various writers with different personalities and views and teaching methods and it shows us that we shoudl focus NOT on the differences but on the similarities.
And as such, we should always take what Christ was recorded as saying over that opinion of any apostles IF there APPEARS to be a contridiction.
I would just note that many times said appeareances is based on how WE interpret certain passages with out 21st century eyes.