Do you know of any traditionally good or even holy sex-themed creatures? I like a good demon girl as much as the next person but sex-themed mythical creatures being evil or predatory all the time seems a bit puritanical.
Blame Plato. The Neoplatonic idea of the material world being corrupt and the spiritual world being ideal has cast a long shadow over Christian thought. So to find good-aligned sex theming, it helps to look outside the Christian world.
In Islam, the houris are celestial maidens that tend to and marry the virtuous in Paradise. There is ample debate over whether these are the souls of virtuous women, or a separate creation a la the angels or jinn, but most scholars favor the latter. Some liberal scholars even go so far as to argue that, because gender neutral adjectives are used to describe them, that houris can be of multiple genders. Likewise, although the Koran is not specific about houris having sex with the faithful in Paradise, later interpretations tend to favor the idea. This is, incidentally, the truth at the root of the "72 virgins" line that Islamophobes like to throw around.
The peris are beautiful winged spirits from Persia, and have been incorporated into lore throughout the Muslim world. They are often associated with love, sex and childbirth. There are traditions of peris and humans in relationships, which tend to end tragically. The peri is in Pathfinder 1e
The apsaras (female) and gandharvas (male, pictured above) are spirits of nature in multiple Indian religions. In Hinduism, apsaras are associated with dance and gambling, and gandharvas are associated with music and divine messages. Both are associated with sex. They are renowned as excellent lovers, and sometimes are depicted in relationships with each other or with mortals. A Gandharva marriage is one based on mutual consent, where a woman chooses her own husband based on love and without rituals. These have ebbed and flowed in frequency based on cultural pressures of patriarchy over the centuries.
The kinnaras (male) and kinnaris (female) are similar. They are more prominent in Buddhist traditions than Hindu ones, but are also celestial musicians and excellent lovers. They are often depicted in male/female pairs as a sign of love and devotion in Burma and Indonesia. I made Pathfinder stats for them here