Well from a DM perspective, there will be overarching plots... but only if you guys want to pursue them. I'm not gonna sit here and say what you can and can't do in this RP. There will be consequences for not doing certain things, sure, but you don't have to do them. Even  if the world was ending and you all decided you wanted to just chill out on your final days or something, it'd be... anticlimactic, but acceptable.

TL;DR: From what I intend, it's as much player-driven as it is story-driven. The story will be there, and the story will also affect the environment according to the amount of action or inaction that occurs from the party.

For example, if there were a barbarian tribe a ways away from town and they were constantly advancing on it and invading, but the party did nothing to stop it and the townspeople were too scared to rise up against them... chances are, that raiding party will be on your doorstep eventually. Just as well the world is in a constant state of warfare and conflict, so things might not stay peaceful forever in the area you decide to inhabit. 

...Crap, my TL;DR ended up being longer than the original part of it. Ah, whatever.

Also since one of the characters is gonna be a Paladin then chances are they're going to be doing SOMETHING against evil and injustice eventually. =P

The RP will be here on the forum, as well. One post a day at the minimum would be my preference. Letting me know if you can't post on a certain day is fine too though. We'll be doing a usual post order that will be determined by... what else? An initiative check before we begin the game.