I guess the only measure you can use regarding that last question is win percentage but that hides many of the other variables involved in defining better or worse. The general level of everyday managers is around 42% (Neil, Wilder, Bowyer, Evans, Jackett) but even some deemed 'successful' managers are below that in the high thirties (Big Mick, NW, Ronnie). Top managers like Shankly are above 50% but as a warning, Alan Stubbs is at 58% due to his longish success at Hibs and disasterous but very short tenures with us and St Mirren.
PW is at 33% which only rises a couple of points to to 35% if you discard the 2016-7 games where he inherited the Stubbs/Jackett aftermath and won just 4/26. I guess in that sense he is vastly underperforming for where he should be in relation to his peers. Nothing that a 46 win season in L1 won't rectify as that would lift him up to 44%