I think you are over complicating things somewhat John.
First, remember that with exception of Gospel According to Luke, the Gospels were not written to convince non-Christians about Jesus Christ. They were written to preserve knowledge of the life of Jesus Christ.
Second and related, with exception of Luke’s Gospel, which was outcome of investigative journalism, all other Gospels were not an exercise in fact finding.
Matthew focuses on Jesus’ teachings, John focuses on the person of Jesus Himself. Mark condenses Matthew for a specific audience. None of these attempt to convince Jesus was a real person. Reality of Jesus was assumed because readers already were believers.
Luke only focuses on stating Jesus as a real person who did exceedingly wonderful things. Remember Luke was not a Christian when he began his investigative journalism. Luke became a Christian in course of his investigative journalism.
Now to the Question at Hand
At timing of resurrection of Jesus Christ, the women already discussed what they saw at the tomb with the Apostles.
At timing of record of what transpired in the Gospels, an Apostle remembers the details — two angels — while another simply remembers the women encountered angels at the tomb. Since an angel is an angel, saying the women encountered an angel, which is not an attempt at giving an exact number, is safe when you are unable to remember exactly how many angels were encountered. Viewed from this perspective, it is easy to see how the difference in accounts preserves authenticity of the historical event.
If writers of the Gospels were trying to deceive, they simply would collaborate to give one account only of the Life of Jesus Christ. Remember Matthew and John were disciples, which is why those two are the unique Gospels. If you read those two gospels — Matthew and Luke — regardless of Luke’s disclosure, Matthew has stamp of personal experience, Luke has stamp of a recount of what has been confirmed via investigative journalism. John of course is the most unique of the Gospels, an inherently personal revelation of Jesus Christ. Since both Matthew and Paul record John to be part of the inner caucus of Jesus Christ, there is external validation for credibility of personal nature of the revelation in the Gospel According to John. The Gospel according to Mark probably was written for people whom Mark believed wanted to get to the heart of the matter of Jesus Christ as quickly as possible without having to sift through lots of other things. Matter of fact people.
The beauty of the Gospels is that in their fidelity to their perspectives, they provide different yet consistent perspectives of person of Jesus Christ. If Paul had not begun writing, we may never have gotten the Gospels. It was when Paul began to write that importance of documenting of the life of Jesus Christ dawned on the Apostles as did importance of documenting their understanding of what it means to receive Jesus Christ as Lord and Savior.
I hope my response helps induce greater clarification in this matter of authenticity of the Gospel accounts.
It seems to me you are interested in truth hence your criticisms of the Bible. Asking questions is something God expects of believers. We cannot believe without faith, but God expects us to have a reason for believing in either of the Bible or the essence of the Bible, Jesus Christ. If we do not keep open minds in our search for truth, however, we can encounter truth yet not recognize it as such because our minds already are made up.
I would encourage you to keep an open mind on subject of authenticity of the Bible and person of Jesus Christ.