I dont these are simply polite visits. There would have to be genuine interest at some level, otherwise, why not pay a polite visit to KC or Seattle? As stated previously, Manning is familiar with the Dolphins facility, and I think he wants the opportunity to step away from the circus of these visits and sit down and talk shop. I think it comes down to Denver or Miami. Denver was a playoff team last year, and therefore is closest to taking the 'next step' and becoming a Super Bowl challening team. Miami has the most attractive pieces in place, a very good defense, a true number one WR (Marshall), a great slot receiver (Bess), a dependable and versatile running game (Bush, Thomas), and a blue chip LT (Long). I think the main questions Manning will have for Philbin will be in regard to offensive philosophy, freedom to audible, LoS calls, etc...
Don't read too much into the dressed down visit, as much as it could look like a courtesy meeting, it can equally look like there are only minor details that need discussing.
As for Matt Flynn...it makes little sense for him to sign until Manning does, unless someone (Cleveland) grossly overpays for him, in which case, they can have him. Whoever misses out on Manning, namely Miami, Seattle, KC and Cleveland (possibly AZ or Denver as well, but they have clearer options at QB) will be in a bidding war for his services. Also, this timeline would make sense for Miami if they had no desire to pursue Flynn in the first place (a distinct possibility). Miami has cap space, but it is limited and we have needs on both sides of the ball. Flynn is still an unproven commodity, and we DO have Matt Moore who played decent. It doesnt make a ton of sense at this point to sink a bunch of cash into Flynn when the money could be spent elsewhere. I'm not saying we shouldnt invest in a QB, just that we shouldnt invest in a QB at the expense of all other positions.