The two words in the title may be poorly chosen, I am at peace with that.
If you approach a project, a body of work, with a firm idea of what it will be before you even begin, it's unlikely to go well. I use "begin" here in a quite broad sense, you "begin" long before you shoot. Perhaps decades, perhaps seconds, but the mental space between the beginning and the first exposure is large. It is in this interval where your conception of what you're trying to do forms. This is the space in which you grasp your subject, wrestle with it, internalize and react to it. It is in this space that the concept of the project is formed.
Doing this in a few seconds is possible but rare. A few hours or a few days is a useful idea of a minimum. But, you cannot begin until you are engaged with whatever it is you intend to shoot.
You cannot conceive of your Chicago portfolio before you go to Chicago, not if you want it to be about Chicago. And if it's not about Chicago, why on earth are you going to Chicago?
Pre-visualization is the process by which the concept is turned, in your mind, into a picture. It's the part after you conceive the project and, ideally, before you shoot, otherwise you're shooting blind.
This is probably best (often? usually? usefully) viewed as a nested bunch of loops. At any step you can always skip backwards one or more steps, and you're probably going to repeat it a lot.
It actually Will Not Work in any other order. Well, you can do something, but you're just shooting bullshit and then digging through it later to see if anything can be found in the mess you've made.