Mm, I agree to an extent that location is a big factor. But I will say IPs are the biggest driving force overall. As you mentioned, GP are there to do 2-3 mazes TOPS. So that means they are entering the event with those mazes in mind. Which ones will they gravitate towards? In order, it'll be: the IP they came to see, then the IPs they've heard of, then the maze with the shortest wait (because they will be desperate for ANYTHING with a short wait at that point), and if somehow they're squeezing a fourth maze in instead of a ride, it'll be the one they have heard is good from a friend who already went or someone they talked to in line or the weird fringe kid in their group who has an odd preference for scarecrows. And while Exorcist was bad (I wouldn't say by far either, considering the abomination that is Pandora's Box was present), it was inarguably the biggest IP last year even while still being a repeat in comparison to Hill House.
It kinda has to be broken down by zones. One maze from each zone will generate huge lines and that will always be the big IP. In the earlier days (06-12), things were a bit more compact so gameplans/early entry was a bit different, but since then, the park is usually split into three (upper lot, lower lot, and backlot) and usually splits up the early entry crowd and the GP crowd in interesting ways. And from 13-16, you had basically one new maze on the upper lot, not counting the HoH.
But split between zones, the driving IPs in 2017 were Roanoke (backlot), Insidious (lower lot), Titans (upper lot).
2018: Poltergeist (backlot), Stranger Things (lower lot), Universal Monsters (upper lot)
2019: Ghostbusters (backlot), Stranger Things (lower lot), Us (upper lot sorta) -- things were broken up into 4 zones and dispersed groups widely
2021: The Exorcist (lower lot), Haunting of Hill House (upper lot) -- strange year, broken up into 4 zones but with low maze count
With the current maze count and locations, we'll be going back to a more 2017 and 2018 vibe, but with 2021 being the layout. That being said, I do think Parisian will still have lowest waits after the opening crush and before Terror Tram closes. However, I don't think it'll be as short as Bride of Frankenstein -- which had very low awareness last year and was like 5-20 mins tops during that time frame. Same time frame for Horrors of Blumhouse, Universal Monsters and Holidayz, it was at least 30-60 minutes but getting shorter. While even the biggest IP on the upper lot will still be the shortest of the waits during the down time, I don't think it'll be as short as last year's...walk ons.