Tool Assisted Speedruns come in many forms. A lot of them are indeed someone simply just playing and retrying segments over and over to get a near perfect human doable time by using the computer to splice the gameplay in its entirety and not just splicing video recordings, but the really time consuming ones have almost everything done frame by frame by inputting movements with a Controller and GUI and pressing next frame, and retries frames when it's not optimized enough.
Some of them also take it incredibly far when it comes to breaking games completely.¥https://www.youtube.com/watch?v=kpk2tdsPh0A
This one is a bit of a meme in the speedrunning community due to the sheer ridiculousness of the required math and the concept of parallel universes utilized to reach the position in the most intricate way possible.¥https://www.youtube.com/watch?v=O9dTmzRAL_4
One speedrunner even learned assembly so he could better understand and dissect how Paper Mario's compiled code works and discover human doable arbitrary code execution to get a credit skip and eventually manage to pull it off in a Real-Time Attack run (at one point before further investigation it even included turning off the N64 and swapping for another game, performing inputs, and then swapping back to original game before the ram managed to clear out of the system.