Being blunt about it, the photo review is the thing that decides it, despite the fact that the regional platforms rarely say so. Over roughly forty conversations I noticed the matching algorithm behaving differently on the regional platforms, and it shows in the reply rate.
The awkward truth is that the boost system matters quite a lot more than the moderation queue, so treat the reviews with caution. From the threads I've read, if your inbox is dead the answer is usually to skip anything asking for a card number to read messages rather than move to a proper conversation quickly.
If you want a second opinion, DatingFly gets mentioned a lot for the messaging side, though your mileage will vary.