There are quite some people who are writing full scripts. That's also what I prefer. It goes like this:

Before creating a single slide, write down sentence by sentence, word by word, what story you want to tell. You can use tools to get a very rough metric of how long your written text will translate being spoken. Stop when you reach your talk length.

Once you are done, you can start creating slides. Choose what you like the best and what fits your story. Few slides, many slides (e.g. Pecha Kucha), no slides.

I would never do live coding but show small videos instead. I have seen live coding fail more often than being a great success. But if you want to do so, have a fallback video at hands.

Now your rehearsal: Not 1 full, not 2 full rehearsals, do as much as you can! For my last and very first talk for a conference I did like 20 full rehearsals, 5 of them in front of people, some in the living room, some in front of the mirror. I bet this can be less in the future but it got me super confident. Rehearsal matters! Don't be lazy and you will be amazed how confident you can go into your talk.

When you black out during your talk, don't panic because you have a full script which you could theoretically read word for word. That always calms me down.

Good luck and have fun.