Re:Monster is a reincarnation isekai that starts off on a questionably sci-fi Earth before transitioning to what seems to be a standard fantasy world… and I’m not really sure why the beginning is so oddly over-complicated. Maybe the author wrote an earlier unpublished series in that setting? Regardless, the majority of the story is entertaining enough with solid action scenes and plenty of deadpan comedy. The main flaw would be the inclusion of the human women and everything related to them, with the elf situation coming in a more distant second (both being egregious fanservice, albeit of differing severity).
A completely different type of reincarnation isekai, Kiwamete Gouman Taru Akuyaku Kizoku no Shogyou takes the unusual path of having the reincarnator get subsumed by the personality of the body they’ve possessed. The result being more of a fanfiction or ‘what if?’ version of a story than an actual isekai, one populated by a variety of overly excitable/perverted characters. It works surprisingly well.