I'm gonna have a 8D 7N trip to Osaka-Kyoto too next month, so far my itinerary is ok not that pack, taking away USJ and shopping allocation (which I have), I think 8D7N for you should be fine. My AA flight also reach KIX around 9pm+, based on what I've read, KIX immigration check may take sometime so I decide to sleep at airport the first night. The rails stop at midnight, but there are limousine bus that still run after 12am but only to a few major hotel in Osaka, so not convenient for me as I book AirBnb in less central area.

Osaka - kyoto trip 8d7n should be enough cause you minus USJ dy.

Last june, went to japan and I arrive early in the morning at 7am. Check out and everything was fast and smooth. Luggage was already there when we finish the immigration. I landed in KIX and head to Kyoto by train. Straight to an airbnb home i rented near fushimi inari. Like literally really near. Area is housing area which is really peaceful and its near mountain since Fushimi inari shrine is there too. theres two station around the area im staying in kyoto which is good.

manage to visit a lot of famous landmark in kyoto and osaka. You have to plan your schedule. And in japan, its all about walking. philosopher's path is only worth going if its spring or autumn cause i went on summer and u see green everywhere only. not worth going IMO. some temple must pay to go in.