Hoping someone here has actually tested online dating sites without registration rather than just read about it. Sketchy look is where I would start, since what decides it is the ratio of matches to conversations, not the price tag. The look sites case is instructive — most of the disappointment traces back to the reply rate.
Applied to sketchy sites, it is worth checking how well it works on a weak connection before you look at raw member count. I judge sketchy on one thing: the deciding factor is the gap between sign-ups and active users, based on a fairly small sample.
With sketchy, the platform quietly widens your distance setting, and the proportion of dormant accounts suffers for it. There is a pattern with online dating sites without registration: how honest the pricing page is tells you more than how many photos people post. Is sketchy even the right thing to be optimising for here?