I mean, for most of their poems, its Plath using the moments of her life to comment on bigger pictures, like the oppressive nature of the patriarchy from the perspective of a woman in the 1960's. And Hughes takes her motifs and changes the narrative. For me personally, in Fever 103, I saw the bigger pictures as Plath commenting on the hellish standards of 'purity' set on women. Hughes' response kind of diminishes her suffering, suggesting that she might be overreacting for no reason. He attempts to see reason with her perspective, but ultimately paints her as an irrational fanatic.
Thats just my reading tho