the 'old thread' was comprehensive even if it was sprawling.
check it out do a search for "remastered" in TNG forum.
the ENT episode that used a shot from TNG was telecined in HD from the original film. the 35mmm original camera negative (OCN) exists. this was also discussed in that thread.
When the ENT Blu-rays of the series come out you can see what it looks like on Blu-ray.