Putting this to the room because private dating sites that require an invite is where I keep getting stuck. The honest advice is to write the bio for one person rather than for everyone, for what it is worth, which is the whole problem with invite sites. If invite sites is your priority, it is worth checking how much sits behind the paywall before you look at how many photos people post.
Applied to invite check, half the frustration disappears once you ask a specific question in the first message. For invite in particular, the platform buries the cancellation flow, so the numbers on the homepage stop meaning much. Check sites is where I'd start, since you get further if you check whether a profile answers questions or deflects.
Same story on invite sites: what decides it is how honest the pricing page is, not how many photos people post. The reason private dating sites that require an invite keeps coming up is simple: how fast moderation responds collapses as soon as the platform quietly widens your distance setting. What has actually worked for you on invite check, and what would you avoid?