Okay, where to start ...

Apparently Charles II had a full wig. George IV gifted some from his mistress to a sex club.

The wig of Charles II is apocryphal. So, in the 1730s a club for gentlemen who wanted to drink, party, and have sex was started in Edinburgh called the "Beggar's Benison" (if you want to know more about the "hellfire clubs" of the day, you should ask a new question because I can't give you much there), where there was reportedly a wig made from samples of pubic hair of each member's wife or mistress, which was worn by the leader. In 1775, some of the members split off and formed the "Wig Club" around a wig made out of the pubic hair of Charles II's mistresses. Said wig no longer exists. There are no records of what happened to it in the century between Charles's death and the birth of the Wig Club. And there's no reason to think it was real. (The one source I can find that goes into detail on it makes no sense, saying that it was made before Charles went into exile during the Interregnum - so, like, before he was 16 [edited from 18, because I do math gud], which is already a little unbelievable, at a time when wigs weren't even the fashion. When wigs did come into fashion, they were long and luscious, and a wig made of pubes would just be hideous to their standard of hairdressing as well as our own mores.)

Another bad pop source says that then the Beggar's Benison club went out and made a wig of their own from the pubic hair of George III's mistresses - a very problematic suggestion because George III was famously a devoted husband who didn't have any mistresses. More realistically, when George IV visited Scotland in 1822 he gave them a snuffbox with the pubic hair of a mistress, an artifact still in the collection of St. Andrew's University; he'd been made an honorary member from afar in 1783, so he was likely well aware of the club and its sexual practices, and collected and donated the hair very deliberately.

Women might gift it in a love letter.

The only reference to this that I'm aware of is a letter from Lady Caroline Lamb to Lord Byron in 1812. The pair had engaged in a torrid but short extramarital affair over the course of that summer, writing constantly to each other during that time. Byron was kind of a jerk and tried to ghost her when he was tired of the relationship, but she was not ready to let him go and continued to write despite the lack of response. One of the extreme acts she resorted to when trying to win him back - in addition to trying to kill herself in front of him - was to clip some of her pubic hair and include it in a letter. She was unsuccessful. As far as I know, other women did not do this and it was not by any means just the kind of thing that might be normally sent as a token of affection.

It seems that even as materials for removing hair (and the gender-rolled desire to do so) were emerging

This is actually a misconception that's crept in here which somewhat undermines the entire question. We have very little evidence of body hair being considered masculine and unwanted during the early modern period; Reading Sex in the Eighteenth Century: Bodies and Gender in English Erotic Culture quotes a poem that extols the beauty of different women's pubic hair, and notes that many texts describe the hair as an inherent part of the female genitalia. In some cases, they praised it as a kind of veil that preserved feminine modesty even in nakedness. It's the early twentieth century when we start to see ads specifically targeting women to sell razors, and then the use of waxing, sugaring, and other chemical depilators on the armpits and legs. Hair on the face was certainly unwanted, but underarm, leg, and pubic hair were simply expected parts of the naked female body in the sixteenth, seventeenth, and eighteenth centuries.