I'm not sure I understand what you're saying about the "6 days versus about 8 days" possible inconsistency - is it not describing the same journey with the same starting and end points? Is that clear from the text? If it's not describing exactly the same journey then maybe you are right? There is still the problem of who is observing these events as they happen but that does not relate to any alleged inconsistency. It only relates to the truth of whether the event took place or whether it's made up.
One final point that I am interested in your opinion on - it's not another alleged inconsistency, it's something that reads like an outright error and it bothered me a lot during my deconversion. Matthew Chapter 16.
24 Then Jesus said to his disciples, “Whoever wants to be my disciple must deny themselves and take up their cross and follow me.
25 For whoever wants to save their life[
f] will lose it, but whoever loses their life for me will find it.
26 What good will it be for someone to gain the whole world, yet forfeit their soul? Or what can anyone give in exchange for their soul?
27 For the Son of Man is going to come in his Father’s glory with his angels, and then he will reward each person according to what they have done.
28 “Truly I tell you, some who are standing here will not taste death before they see the Son of Man coming in his kingdom.”
Jesus is talking to his disciples and it reads like he is referring to Judgement Day and his Second Coming, yet he appears to be saying that that will happen within the lifetime of his disciples, which is clearly wrong because we are still here in 2019.
Here are the three texts:
Matthew's says:
Mat 16:28 Verily I say unto you, There be some standing here, which shall not taste of death, till they
see the Son of man coming in his kingdom.
Mat_17:1 And
after six days Jesus taketh Peter, James, and John his brother, and bringeth them up into an high mountain apart,
Mark's says:
Mar 9:1 And he said unto them, Verily I say unto you, That there be some of them that stand here, which shall not taste of death, till they have
seen the kingdom of God come with power.
Mar_9:2 And
after six days Jesus taketh with him Peter, and James, and John, and leadeth them up into an high mountain apart by themselves: and he was transfigured before them.
Luke's says:
Luk 9:27 But I tell you of a truth, there be some standing here, which shall not taste of death, till they
see the kingdom of God.
Luk_9:28 And it came to pass
about an eight days after these sayings, he took Peter and John and James, and went up into a mountain to pray.
These are not in contradiction. They are saying the same thing, from two differing angles. Consider:
"after six days" =
the 7th day (the word 'after' means that which takes place in a following position, even according to Thayer's Lexicon)
"about an eight days after" =
the 7th day (the word 'about, means approaching or 'nearly', even according to Thayer's Lexicon)
The saying:
"six of one, half a dozen of the other" comes to mind.
As to the second point, Jesus is referring to the final day. The events that transpired, are but a type, a faint shadow of the final "Day of the LORD", when the Translated (as represented by Elijah) and the Resurrected (as represented by Moses) will be together with Jesus in glory, as it is written,
1Th 4:14 For if we believe that Jesus died and rose again, even so them also which sleep in Jesus will God bring with him (ie back to Heaven to the Father).
1Th 4:15 For this we say unto you by the word of the Lord, that
we which are alive and remain unto the coming of the Lord shall not prevent
them which are asleep.
1Th 4:16 For the Lord himself shall descend from heaven with a shout, with the voice of the archangel, and with the trump of God: and the dead in Christ shall rise first:
1Th 4:17 Then
we which are alive and remain shall be caught up
together with them in the clouds, to meet the Lord in the air: and so shall we ever be with the Lord.
Peter speaks of the mount of transfiguration event in his own epistle:
2Pe 1:11 For
so an entrance shall be ministered unto you abundantly
into the everlasting kingdom of our Lord and Saviour Jesus Christ.
2Pe 1:16 For we have not followed cunningly devised fables, when
we made known unto you the power and coming of our Lord Jesus Christ, but
were eyewitnesses of his majesty.
2Pe 1:17 For
he received from God the Father honour and glory, when there came such a voice to him from the excellent glory, This is my beloved Son, in whom I am well pleased.
2Pe 1:18 And
this voice which came from heaven we heard, when we were with him in the holy mount.
2Pe 1:19 We have also a more sure word of prophecy; whereunto ye do well that ye take heed, as unto a light that shineth in a dark place, until the day dawn, and the day star arise in your hearts:
2Pe 1:20 Knowing this first, that no prophecy of the scripture is of any private interpretation.
2Pe 1:21 For the prophecy came not in old time by the will of man: but holy men of God spake as they were moved by the Holy Ghost.
Notice how Luke describes the scene:
Luk 9:29 And as he prayed, the fashion of his countenance was altered, and
his raiment was white and glistering.
Luk 9:30 And, behold, there talked with him two men, which were
Moses and Elias:
Luk 9:31 Who appeared
in glory, and spake of his decease which he should accomplish at Jerusalem.
Luk 9:32 But Peter and they that were with him were heavy with sleep: and when they were awake,
they saw his glory, and
the two men that stood with him.
So it refers to the immediate moment (Luke 9:27), as a type to the greater event (Luke 9:26). In other words, a miniature picture of the grand finale. In fact, John who was with them, even later also saw in vision, the final events (Revelation).
Jesus also speaks of 'seeing' (which deals with more than simply the physical eyeball, but the understanding of the heart/mind, see Genesis 3:5-7) the Kingdom of God, by faith, even though Peter, James and John got a snapshot of it by their eyeballs:
Joh_3:3 Jesus answered and said unto him, Verily, verily, I say unto thee, Except a man be born again, he cannot
see the kingdom of God.
This is repeated throughout John 3.