Usefulness of VBW in spectrum analyzer
Do you have any hands-on experience with a spectrum analyzer ?
If not then maybe you should as it will give you a better understanding of the effect of changing the RBW and VBW.

Ad 1) Indeed the VBW setting can be used to filter out noise and "smooth" the graph. The information is not so much "wasted" but "averaged". Most spectrum analyzers also have an option to average but this averages over multiple traces, this takes longer time and is inconvenient for observing a short event.

Ad 2) Normally you would leave the analyzer on auto settings and then it will take care of the RBW and VBW settings for you based on the frequency span you select. There are no guaranteed settings so that you don't miss anything ! Depending on the signal you're looking for you determine what settings you should use. This requires some practice.

I have been using spectrum analyzers for 20 years already without really thinking too much about how they work. I consider them basically a tunable radio receiver with a visual output.