This is our go-to week (also coming from Canada) to visit UO or Disney, having been at least seven or eight times the end of August.
We always stay at the Royal Pacific, as it is one of our favourite hotels, regardless of EP. But frankly, given the low crowds, they don't reduce the waiting that much. And with the notorious August heat we also spend a day at VB, where the hotel EPs don't apply - so if you do the same (which I would strongly recommend if you like waterparks at all) that's another reason to skip a premier for CB, which is basically attached to VB.
Our last end of August trip to UO was in 2021. Keep in mind COVID was still impacting crowds, but it was DEAD. Like spooky quiet, to the point where at times, like at VB, it almost wasn't as much fun (for the first hour we basically walked around an empty waterpark). The only time we ever waited for anything was for Hagrid's and VC, and neither of those took EP anyway.
HHN opening night that year (as it will be this year as well) was the Friday of Labour Day weekend. That was our last day, and it actually had the lowest crowds of the week - during the day. Makes sense if you think about it - people will flock to the park that weekend for sure, and the hotels will fill up, but if you're going for the Halloween event (we weren't) it's unlikely you'll be lining up at 8AM for EE, and you may skip the parks during the day altogether, knowing you'll be on your feet all night and up until 2AM.
We're doing our first HHN this year, arriving the last Tuesday of August, staying at RPR through Sunday. Can't wait - maybe we'll see you there!