Hey, @Don Kasper! I would say I played with a "relaxed" touch, but not light (exceptions to come). I subscribe to my theory that the "big sound" comes from the coordination of right- and left-hand, and a quick stroke "through" the string. That's more of the Dave Holland method (I took lessons with Dave). There are a lot of other ways to play right-hand pizz, and this is one of the ways that I most often use.
For an example of an alternate way of attacking the string, we can watch Ray Brown "pulling" the string and letting it snap ... also great, and he's one of the masters without a doubt. (I sometimes use the "pulling" technique with the r.h., but my default is the loose r.h. wrist, and the fast snap through the string).
I have to read a lot of music in my day-to-day work, and arrangers will write dynamics that they expect to hear. The difference between pp, p, mp, mf, f, ff is the amount of flesh of the right-hand finger that is going through the string. The volume is determined by the amount of finger-flesh that I'm using.
The speed of the stroke through the string (r.h.) and the coordination with the left hand also makes for the "big sound," (medium & uptempo) or for the "warm tone" (ballad playing). For me, I usually strike through the string fast whether I'm playing a ballad or an up-tempo walking line. For a ballad, I might play "lighter" with the r.h. to achieve a quieter dynamic, but the tone, pitch, and time would still be precise because I'm coordinating the right- and left-hand. For a medium tempo, I will use more r.h. finger, but still strike through the string fast, coordinated with the left hand. For an up tempo, I might use a bouncy right-hand wrist, and the l.h. and r.h. are very coordinated (hopefully like you see in the video). I might switch to two finger with the r.h. if it's very fast.