I thought the story ended a while back, when it was established that there is no way to tell them apart by looking at them. How can you tell geography when looking at a plant and/or flower? And besides, Paphs and some Cyps both are from Asia, although not in the same habitat. Phrags and Selenipedium are both found in South America.
Looking at a lot of flower pictures you could play an odds game.
1) 90%+ of cyps have large balloon shaped pouches (lips). A couple species like C. gutta have rimless bucket like pouches.
2) 90% of paphs have rimless bucket shaped pouches. The parvis (about 10% of paph species) have balloon like pouches like the bulk of cyps.
3) 80% of phrags have a bucket shaped pouch, but with a "liner" all around the inner rim of the pouch. Granted this liner is often hard to see in standard frontal orchid porn flower photos. Besseae, Kovachii, and the schlimii group are notable exceptions with more cyp like balloon shaped pouches. However besseae and kovachii flowers are so distinctive and famous now they should be easy to remember.
I saw a previous mention of how schlimii/fisheri flower pics could be confused with delenatii/vietnamense (or for that matter Cyp. reginae) if just looking strictly at flower pictures, but we are only talking 5 of the ~150 or so species of Cyp/Paph/Phrag.
To me, all selenipedium flowers look like cyp flowers, but its rare to ever see a pick of a selenipedium flower anyway. So I wouldn't sweat those odds.
Mexipedium has a cyp like balloon shaped flower, but with the exception of say delenatii alba, (or any albino cyps), the odds would be good that you would be able to spot this one in a photo line up.
If you get to see the plants in person to look at flowers from several angles and also see the plant/leaf habit your odds can go way up.