You're correct on the first point, and it's worth adding that Interac is a closed network - Interac has no obligation to let anyone participate, and it's been a pain point in the FinTech world that you either have to convince them to let you in (e.g. Wealthsimple) or piggyback on a banking partner (e.g. most other FinTechs.) Maintaining that banking relationship is a big burden for fintechs, especially if you rise to a level where a bank views you as direct competition.
RTR's membership requirements are set by PayCan, who have a mandate to foster competition. Any FinTech who can meet requirements can, in theory, hold a settlement account on RTR and participate. Interac has an incentive to keep the club small, so to speak, and prevent new up-and-comers from cannibalizing their market share.
From a competition lens, the hope here is that RTR levels the playing field for both the big banks and fintechs and opens the door to a lot more consumer-facing innovation. That will, of course, depend on the network effect and who gets onboard.