I outline to a detailed but not specific way, running out the proposed action without worrying about how many chapters there are (because word count is approximate until actually in production).

And then, once I start to write, and the story takes on its own life, I let go of the outline except as a periodic "did I forget any plot threads" reminder.

Rather than pantsing or planning, I call this architectural gardening: you put the plants in the right place, and then only have to prune them back once they start to do their own thing.