Really, all you'd be asking is "do worse pitchers have shorter / more shallow peaks?". And the answer, in general, would be "of course".
A pitcher with a 7 k/9 and a 3.5 BB/9 = very mediocre, and possibly quite s***** depending on other peripherals like GB%.
In general, a pitcher with a lower walk rate is better. Better pitchers can decline a bit and still be given opportunities, since they're still effective relative to replacement level. Pitchers who walk more hitters, in general, are worse. When they start to decline they lose opportunities fast. Their peaks would be shorter and end more abruptly.
But that doesn't mean that their talent peaks are any more shallow. They'd just cross a threshold of opportunity.