I've for some reason always suspected that the Q are what the El-Aurians are going to eventually evolve into. It doesn't explain what Guinan thought she could do to him with her claw-hands, but it would provide a good enough reason for Q not to just fingersnap her out of existence. It would also make for a plausible explanation for Q's fixation on the Borg, him trying to teach his kid not to meddle with them, and why the others don't approve of his messing with the universe at large at all. Wouldn't want to inadvertently manipulate themselves out of existence. But aside from that, once one's evolved to the point where even time no longer has any grip on you, it's prety easy to make the claim that you've always existed.
As for the Preservers being the first, the Q might've simply never shown themselves. Theorethically, considering how many civilizations in Star Trek at some point develop time travel, there could've (and probably would've) been observers from thousands or millions of species from the milky way alone, hailing from every point along the universe's existence, studying the Preservers and taking equally great care not to reveal themselves. At the very least, they got mentioned by the Preservers about as much as the Q.
On to another thing that has been puzling me.
Q seems to believe that humans might one day advance further then the Qs, or atleast have the potential to do so.
Is there reason to believe that the further you travel into time, the more uncertain that timeline is the correct one?
And Qs worries are founded in fear of what might happin in the future?... Or might not happin...
edit: excuse me, if the questions are more then just trekkie questions and lean on a teoreticphysisistly one instead. (uhh big words - english isnt my native language - pardon my spelling)