Put me in the Ortlieb camp. They have a good solid mounting mechanism that is easy to remove and install. And when they say waterproof, they are exactly that. You could roll them up and use them as floats if you were so inclined.

As to the organization, I organize them with ziplocks. I started that practice before I got the Ortliebs because my old panniers weren’t water proof. Frankly, I like the bucket like nature of the Ortliebs. I never found the pockets on my old panniers to be all that useful. Nothing really ever fit in the pockets all that well so there was a lot of wasted space. I use bikepacking bags now as well (not on the same trips) and that’s the biggest problem I have with them as well...too many small cavities where things just don’t fit.