[Question] Footprints Scheme

First I have to say that I'm not that experienced with GSA SER but I'm learning it step by step. I'm using Scrapebox for link harvesting. My question is though I have to create footprints to harvest register pages (for e.g. "Powered by vBulletin" + inurl:register.php) or threads with an answer function (for e.g. "Powered by vBulletin" + inurl:newreply.php)? Is there a difference between both cases? Will GSA SER post an answer to a thread after registering or posting a new one? I hope you understand what I'm trying to learn. If something is unclear just ask me.