I have trimmed a number of WB' s over the past few years, all I do is remove the ring and trim the whisker with a pair of side cutters. Remove until you have a flush rear portion. Yes trim them as close to the ring as possible, the point is to remove excess whiskers and the hole size should be left the same to properly hold the arrow shaft in place.

Never tried nail clippers but as long as they are sharp they should work fine.