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Succubi have an Ecology article in one of the 400s issues of Dragon Magazine, which goes into greater depth about their nature. They are fallen Angels of Love, who actually signed up with Asmodeus' rebellion against He Who Was because they wanted the freedom to share and inspire love as they saw fit, rather than only doing so as directed by He Who Was. Ironically, when they were transformed into devils, their capacity for love was inverted, leaving a yawning spiritual void in their hearts; this is the source of their ability to drain souls, as they can literally siphon away the souls of others to try and fill the void and stop feeling so hollow and empty.
Incubi also exist in the World Axis, and make their presence felt in the 4e Demonomicon. Here, they are succubi who followed Graz'zt into the Abyss, and have since been transformed into demons. As such, they still retain a devilish knack for charm, manipulation and deceit, but are much more savage and impulsive. Incubi are able to shapeshift between the forms of fiends, mortals, beasts and dreams, and use these talents rather than the more covert enchantments of their kin to establish fiend cults or toy with mortals. As with the succubi, nothing explicitly says that incubi have to be male in the Demonomicon, which means - to me - that female incubi and male succubi are equally possible. This is a huge improvement over the 3e and Pathfinder version of the incubus, which is literally and explicitly the demonic incarnation of rape, and are thusly mostly used as brutal and expendable soldiers by the various Demon Princes and Queens.
I think you're right, the trick to Charming Kiss is to have the succubus use it on an NPC ally of the PCs. Or really use it on any NPC that for whatever reason the PCs do not want to see harmed. Now it becomes a puzzle of how to separate the two so you can actually attack the succubus. Which IMO is a much more interesting scenario than telling one of the players they're not in control of their character for a while.
There's always the option of giving characters rewards for going along with charm effects, like gaining a fixed amount of XP or getting temporary buffs based on how cooperative you're being. It means you've got a reason to (a) fall under temptation and put the party at risk, and (b) break free at the critical moment, turning the tables and saving the day. Which aren't terrible things to happen.