Not everything works for everyone. If preparing too much (does sound contradictory) makes you crack under your own pressure then it doesn’t work for you. When you are preparing is it possible to focus less on exact wording and more on your main ideas? There’s different ways to say the same thing, we all know it here. Preparation is important but you don’t need to be an actor following an exact script. Especially in an interview you can’t plan for everything, they will probably ask questions you didn’t prepare for and that’s fine. For interviews in particular it’s best to practice with a partner. Someone who can throw questions at you and give feedback on your responses. A friend, family member, if you’re lucky a kind stranger on a video call. Best of luck with your interview, clearly you already have been preparing so I have faith in you. Hopefully you don’t need to follow my advice because you will get the position!