I don’t even see how he would harm the PK
What’s he gonna do, make a big fist and punch him? The PK tanked a blast that evaporated 3 seas
And yeah Luffy isn’t a cartoon character just because he’s like rubber. A cartoon character would be able to build like a planet destroying ray in a few seconds, or literally just grow wings and fly at the speed of light or something (or take a nuclear blast to the face and only be blackened with messed up hair)
That’s not really toon force, and even if you were to consider it that then it would probably be the very lowest levels of it. When you think of toon force you typically think of the ability to literally warp or deny the reality of the medium that you live in. For example how loony tunes characters can paint a road in a wall and it becomes a path, pull or reach into the next panel of a comic, or interact with things that should be metaphysical like onomatopoeias/thought bubbles.
So far the extent of toonforce that luffy has displayed (outside of normal applications and amplifications of his abilities) is the classic running on air gag and creating goggles from his hair, and while those can be pretty impressive for the one piece verse they’re not exactly the strongest feats of all time
Tldr: luffy doesn’t necessarily have insanely powerful toon force, he mostly has his normal powers but amplified to a sillier level