I am not an experienced Japan traveler but I have been through Kyoto a couple of times. I stressed quite a bit my last trip over whether to fly from ITM or KIX to OKA. For me it depended on many factors but ultimately I decided the easiest was to fly from KIX especially since my hotel was in the Kyoto station complex. From Kyoto station you can take the airport express Haruka train direct (a couple of stops) to KIX and since it is specifically an airport train it has plenty of luggage space (luggage racks near the doors plus the overhead) and I was traveling with family and had a lot of luggage.

For me I was worried about uncertainty of getting bus tickets to ITM, finding the right pick-up location for the bus to ITM, and since I was leaving early in the morning if I screwed anything up and missed my bus I would miss my flight. Finding Kyoto station is easy. Any taxi can take you there and once you are there it is easy to get tickets on the Airport Express Haruka direct to KIX and Japan train schedules are like clockwork so I had much higher confidence in not missing my morning flight from KIX. If I had a later flight in the day I could have built in a time buffer and tried for ITM but so long as you do not mind the slightly longer travel time to KIX the stress level is lower taking the Airport Express Haruka.

https://www.westjr.co.jp/global/en/t...ess/train.html
https://www.westjr.co.jp/global/en/ticket/icoca-haruka/