Against a backdrop of brand logos, plastic pint glasses and corporate away-days, people wonder whether the real Edinburgh Festival Fringe still exists. The festival has swelled to an untameable 2,871 shows, most of them well-behaved and aspiring. It’s time, some say, for a fringe of the Fringe.

So, it’s only fitting that questions of authenticity and artifice are being asked. First there’s David Leddy’s Long Live the Little Knife at the Traverse Theatre (until 25 August), a caper in which a pair of con artists (mostly trading in fake handbags) move into major art forgery. Or rather art-forgery forgery, because their plan is to pull off a huge con, come clean and then live off the kudos. It’s the perfect crime, as Jean Baudrillard might say.

The play prods at the terms “real” man, “real” woman and “true” love but its main target is the free market. It triggers a race to the bottom in which scammers scam scammers, who scam other scammers. Though Leddy occasionally trips into clever-clever territory and starts to irritate, he has brio, toying with the show’s authenticity through scenes written in the style of verbatim theatre and in accents from around the UK. A world that eats its own tail, he suggests, will ultimately consume itself and disappear.

There’s another great faker in Kubrick3 at the Pleasance (until 26 August), a play about Alan Conway, who posed as the reclusive director for several years (and inspired the 2005 film Colour Me Kubrick). Conway bedded students, hobnobbed with Julie Walters and gave interviews to the New York Times, although he’d only ever seen half a Kubrick film (he walked out before the end). David Byrne’s impish production makes canny use of four actors – three female, one male – as a hydra-like Conway, back from the dead, ashgrey and running circles around his son. The play is scruffy and small but its well-honed gags and gusto are ample compensation. It has an intriguing philosophy: if life gives you lemons, grab someone else’s limelight.

Kieran Hurley’s and A J Taudevin’s Chalk Farm, at the Underbelly until 25 August, is a serious rejoinder to the constructed narrative of the summer 2011 riots. We have been spun a story of mindless violence and poor parenting; this disruptive piece refuses to swallow it. Jamie is watching on the telly. His neighbourhood looks like a film set. The itch to get closer, to join in – let’s face it, we all felt that – proves too much.

Outside, kids carry goods in bulk. Jamie nabs a gift for his mum. History is being made, even if no one can quite articulate the causes. It’s a class thing but not in the way the papers and politicians make out. Chalk Farm is guilty of beautifying mayhem but it understands without excusing and is fierce and fixed in its gaze.

In Have I No Mouth at the Traverse (until 21 August), Feidlim Cannon attempts to heal his family’s wounds. Onstage with his mother – a reiki master – and their psychotherapist, Cannon invokes the circumstances of his brother’s death in 1984 and then his father’s in 2001. The latter was preventable. Totemic objects – a natty doll, photographs – and reenactments build a charge and when the psychotherapist, his head wrapped in bandages, stands in for Cannon’s father, it’s as raw as anything I’ve seen onstage.

Watching Have I No Mouth is a challenging experience. Whether the play is being staged for the benefit of its participants or ours, I’m not sure – it makes you feel their pain, rather than soothing yours. Yet it’s hard to dismiss this display of their agony as indulgent. This is theatre with undeniable force.