I agree with the photos aspect. Guys with eye-catching photos can get away with more. The good news is, you don't have to be superfit or goodlooking to have such photos. Just put more work, time, even money into your photos than the avg. guy (see the theme here guys?) Photos are huge. They allow us to project an image--which is exactly what the chicks do.
No reason ever to wait to invite them though. My best initial email compliments their sexiest-looking photo then invites them for a drink or two--on a specific day and at a specific place and time. I believe that "Quality" is impossible to judge in the deep early phases of courtship. But the women I meet (and I've met a LOT via online) are generally independent, impulsive, and very interested in sex. I look upon these types as admirable. They are today's conquest and the wives and moms of the future. All in one. It stays with them their entire lives. Women--and people in general--are often complex, and contradictory. I know I am.