I would do a few things to help you find the best pressings
for one look myles Astor of audionirvana hope thats spelled close enough. He is a walking amazing talent on analog sources. Gary koh as well.
also there are non audiophile you tube videos
when I was looking for good pink floyd that guy was great. He said why and described why then showed markings and all you need to look them up.
i hope this helps you.
The major issue with getting an original pressing is that there are almost none that are in mint condition, something you can easily get with the reissues listed above. So regardless of the sound quality differences in mint versions of original vs. reissue, the originals that you can buy are not going to be mint unless you have infinite patience and close to infinite money.
One important point about the KOB issue. When originally released there was a speed error in the playback of one side (or one cut). That made the side or cut too fast or too slow (someone put in the correct details.) As I remember it was later discovered and when Classic Records did their audiophile reissue 30 years ago, they did correct the problem (I remember they had two versions on the reissue, one at the original speed and one at the corrected speed - IIRC maybe 1 or 2% different).