I think the best reference is Stefan at CncKitchen
He mostly sticks to industry standards so that measurements are comparable and is as close as it gets to scientific standards for a non-commercial environment.
I made a small jig and specimen to just evaluate layer adhesion of different filaments at different print settings. but that was tailored to my needs and willingness to invest time and money. So my numbers are not comparable to anyone else’s. You can find the description and results here: Various PETG brands compared
I did a few more tests in the meantime. Most noticeably I couldn’t reproduce the good results with Sunlu. Even after drying again, it was about the same as most other brands. I have the feeling, that maybe in the first test i had slight over extrusion and that made the specimen stronger.
But I didn’t persue that any further.