GoPro give you firmware updates to the cameras for free, so there’s no ongoing cost after purchase except for different mounts. The editing software is included with the camera and auto detects/asks if you want to update. It’s ideal for a quick video edit or export, but is by no means a pro level editing program.
I’ve only played with the session camera for a few moments. You can change the settings using the app on your phone, but I don’t think that there are buttons to do it on the actual camera, which I can see being super annoying if you want to quickly switch between photo and video. An advantage of the bigger version I have is that I can change modes and make any tweaks to the video settings (resolution, ISO, frame rate etc) on the camera itself.