The saucy bits: Explicit sex, including D/s power exchange, bondage, blindfolding, edging, anal sex, oral sex, and dubcon (essentially a lust spell cast on the MCs by a side character), as well as size difference, an age gap, and flirting over 50s bodice busters and the feelings wheel.
The serious stuff: Discussion of eugenics (including infanticide) and violence (some toward children), attempted genocide, child abuse, intimate partner abuse (not at/from/between MCs), federal boarding schools, cultural erasure, racism, and xenophobia. On screen mental illness, panic attacks, cannibalism (not by MCs), ritual sacrifice (not by MCs), apathy about dying that may read as suicidal (by an MC), past suicidal ideations, anger management issues, and depression (by an MC), regular threats of violence (absolutely by the MCs, as well at toward the MCs).
Also: Snark, healing, family both found and blood, and a deep, loving, affirming relationship between the MCs.
HEA? Our MCs get their well-earned happily ever after, with a cliffhanger on the future of Faerie. Because overarching plot.