Human performance experts have known that visualisation and mental rehersal improve results.
If your game allows it- do it. The trick is being able to use the information gleaned in the walk through to make a plan quickly, retain that plan and execute it the way you thought it out. Of course... if a person cannot do that- it could make things worse. And we tend to watch others, and out plan goes out the window- creating other issues when our turn comes up.
IDPA... you get a description of the COF... the rules say no "air gunning" and the "walk through" does not exist as we do it in USPSA 3 gun, etc.
IDPA would be even better in theory if the other shooters did not see the COF shot... the idea is to get it in "one take" as it where.