For me, I need to have an idea of how the whole plot needs to look before I start writing the first line. 
It doesn't mean that I outline every single little thing that has to happen. But more of a general plot arc - who are the characters, what is the story concept, what are the main conflicts, how do I want it to end.
Then, I do a deeper dive. How do I get them from the start to the conflict? How does the conflict get resolved?
It's like slowly filling in the plot, one layer at a time, each time going deeper and in more detail. Where you want to stop is up to you. For me, I stop when I outline 10 chapters or so (or less, it varies). Those chapter outlines are not fixed either. I've changed lots of details if the character has evolved or the pacing seems wrong or I didn't take something into account in the original outline. But broadly speaking, it doesn't deviate from the main plot arc.
Plotting is very beneficial in my opinion!
I think it works wonders for pacing and seeding clues. On the more administrative side, it also helps if you want to know when to drop a Q&A or when is a good time to do promotion, scheduling, etc.