I have dabbled in the Niagara region for a while, so I can chime in with some observations.
There are still a few reputable indys working in the area. I have not sampled any of them as of yet, so I can't offer any personal insights, but they do generally get good reviews elsewhere (Google is your friend). I have developed a close connection with a former indy who is no longer in the biz. We see each other from time-to-time and did a vacation together a few years ago (made it home just before the pandemic closed everything down). We're kinda fk-buddies now.
In terms of agencies, as previously noted, Temptations and Diamonds are now owned by the same person. Diamonds tends to be the 'farm system' for Temptations. Elite is the other agency. Ladies I have met with include Lana, Anya, Grace, and Alice from Temptations (the latter my fave), and Alex from Elite. All of these ladies I would recommend.
Unlike many of the Toronto agencies, you don't see a lot of advanced schedules. Elite has started to post some advance availability, but Temptations/Diamonds is basically a real-time availability posting.
One other observation about the agencies. While they may advertise incalls, in reality they just rent hotels rooms for that particular appointment, so it feels a bit like an outcall where the lady just gets there first. The exception to that is Temptations / Diamonds, which has a dedicated motel room in the falls. That allows them to have a more ample supply of towels, bottled water, etc. The downside of that, though, is that it's only one room, so if there are multiple overlapping appointment requests, booking can be a challenge which is frustrating for both the ladies and the clients.