I don't think trickster is positive. At best it is neutral. I would never consider it to mean "flexible, boundless, smart". A trickster is someone that plays tricks. That could be tricking people into losing money or property. It could be tricking them into doing something that is bad for them. At the neutral end of the spectrum, it might be something like playing pranks on someone. You make a fool of them, but hopefully don't do anything to hurt them.

It depends on the context. A swindler is somebody who uses trickery to get money from people; most of their tricks (swindles) at illegal, all are antisocial and bad. The term 'trickster' is much broader; it describes a personality type that uses cunning and defies social norms to play tricks on people. A swindler is a kind of trickster, but not all tricksters are 'bad' or motivated by greed: most pantheons include a trickster god such as Krishna or Hermes who might play the most shocking tricks on other gods or on mortals, tricks which add to, rather than detract from their popularity. Silvio Berlusconi Is an example of a trickster who is a hero for many people (myself not included).

Trickster definitely has a more positive connotation than many of its synonyms like charlatan, fraudster, and swindler. It can be used in a playful way, "Oh you're quite the trickster, huh?" but it generally has a neutral meaning at best. People do not like to be called tricksters.