How closely tied are the characters to the road? 100%. In fact, the road itself is a major antagonist in the film. Many ariel and long tracking shots are effectively used to emphasize the desolation of the highway cutting through desert.
Is the film vehicular or character-based? It is vehicle porn with slight pretensions toward character development. The Charger acts as a memory machine bringing back traumatic events from Kowalski's past. But these are just padding for a film loaded with squealing tires, close-ups of gear shifts and distorted engine noise.
How painfully hip and articulate are the characters? It is 1971, so not at all. The driver, Kowalski, is a tight-lipped, bad ass with no concern for witty dialogue or glib philosophical asides. This stoic mutha' carries the movie.
Number of desolate mythological figures: plenty, 4. The movie plays like a deranged page from a Joseph Campbell textbook:
1. a blind DJ guides Kowalski from a hick town called Kow
2. a nude temptress on a motorcycle is denied sexual advance
3. a dusty old snake-catcher in the middle of the desert bestows
4. a hermit in a remote shack provides the hero with special tools
(and chemicals) for his journey
All of the characters are obvious but not forced and therefore it is fun to hang out with these clowns.
How much embarrassing existential content? a potentially disastrous amount. At one point Kowalski is even referred to as the last person for whom "speed means freedom of the soul." Vanishing Point is a literal application of the "road as liberation" formula. But because it is 1971, post-Altamont, the prospect of fulfillment is grim, and the ending is fatal. Thankfully, the movie's grindhouse naivete keeps these themes playful rather than becoming overbearing.
Can the word quirky in any way be associated with this film? Not at all, it is honest 1970s grit from 42nd street.
Does anyone play the harmonica? No. Soul music is substituted during moments of roadside reverie.
Is it any good? Vanishing Point is a solid chase movie. The Charger is raw, the characters are colorful and everyone is doing drugs. Plus it's barren, ghost town style fulfills the expected cool quotient that Tarrantino gave it by reference in Deathproof.