Creating the Normal Map took many rounds of trial and error. Note to myself: Many of the duplicated geometry appeared as yellow in the normal map. Will need to first reverse it, then Set to Face and then reverse again. Not sure how it works but at least this steps helped resolve the issue.
Following the M1 Garand, I decided to pick a relatively simple subject and tried to go through the whole workflow of modelling, UV, normal mapping and texturing quickly. This project took about two and half weeks.
Went back to Pluralsight to re-learn how to work with Quixel DDO.