In addition to previous answer you can also use Ninjastic.space (made by TryNinja) to get what you are looking for and much more.
I use this tool all the time, and there is also new beta version with even more improvements.
I haven't really used it much since the beta version though but I think it pretty much does what LM is looking to get. If I can remember correctly ninjastic.space actually gives a percentage statistics of how much posts a person has in general distributed across multiple boards on the forum. With that you should be able to narrow it down to their number of topics.
This is actually the very first time I'm coming across this I'll check it out too
however from what I can see it seems only LM's list of launched campaigns are there.