The essential measure of competitive balance in sports leagues is called "Noll-Scully" named in part after Stanford economist Roger Noll. He is unimpressed by the NBA's proposed system changes that he says would have, he says, "little effect" on parity.
He's in lockstep with every other noted expert who has commented publicly, including David Berri, who has studied the subject intensively across all major sports and found that of all historic attempts at harder caps "none of these institutions had any statistically significant impact on balance in any of these leagues."
British economist David Forrest says "the evidence isn't there."
Even the NBA's own expert on the economics, armed with all kinds of evidence tying payroll and on-court success, admits there is, at best, weak evidence to suggest harder caps have led to greater parity in other leagues.
The NBA itself saw no improvement in competitive balance when it became the first major American sport with a salary cap in 1984.