Personally, most of my best scenes (in my opinion) were improvised. I have a rough outline (e.g. MC meets LI, MC is out in park reading, MC bumps into ex) (this is not my actual story haha) and then when I am coding, I think of stuff that spices the scene up visually, so for example I create a falling leaf overlay and direct it, BG characters running around and doing their own thing to make the scene more realistic. It’s not really something you can plan out beforehand, it just comes to mind when you are actually writing/coding it.
As for dialogue, I write it out beforehand, but a lot of the time change it when I am coding it.
I know planning is essential, but when I am actually writing and coding, so many more ideas come to me.