I know that "pack" is reserved for some socially unacceptable stuff like theft etc. Also, a bunch is a group of things that are connected 'a bunch of grapes'. A pack is a group of things that have been packaged together 'a pack of cards'.
Nevertheless, I am not quite sure which which collocations below are natural and idiomatic and whether if they all work, there is any significant shades of meaning between them:
a. A bunch of fools.
b. A pack of fools.
c. A bunch of yes-men.
d. A pack of yes-men.
e. A bunch of thieves.
f. A pack of thieves.
To me, each case in every set is a precise equivalent for the other case in the same group. However, I have always taken them with a grain of salt and that was why I decided to bring a question up here. Please do me a favor and explain the nuances between them (if they exist,) otherwise please let me know whether I have been right taking them as interchangeable collocations.
PS. I know other applications and semantic prosodies of each word listed above e.g. a pack of wolves etc.