I have the original text for my comics which is actually a role play game. This text is edited a lot. The main plot is the same but I add many scenes to introduce and explain the characters to my readers.
Then this text is split into chapters which are almost close to the final results. Sometimes I change the speech because something else might fit better into the speech bubbles. The meaning stays the same though
Then I draw very, very rough sketches to understand my future layout. And then I draw the pages themselves. Sometimes I have cut scenes, most of the time there are jokes, which I'd love to tell, but I remove them because they need additional pages and take too much time of the main plot. But I draw them later as bonus materials and post on my Patreon.
Sometimes I have to change the frames a bit, because I can change my mind about the perspective or something else. And once I've decided to turn two pages into one because they had too few information on them. But most of the time the result and the draft are very close in layout
Once I did an awful mistake. I had my original script, but took my reader's critique too hard and tried to change the further pages considering their critique. The difference was huge and now I see that I failed the scene completely. That's why since then I use my original script only and prefer to follow it
I've actually tried to draw chapters in three different ways: with very detailed script, with simple script (just dialogues and basic descriptions) and with no script at all. Simple script works the best for me, though it differs slightly from the final result. However, this result is always better than the original, because text and sketches allow to see most of my bad decisions and change them