The pictures do look genuine to me, they look like the ones I bought and used on my phones. There shouldn't be a problem if you grab one of those.
As for the gaskets, they come off quite easily, and it shouldn't be a problem should you find yourself unable to recover it from the old screen. I think I made a mistake and they were actually made of rubber, but I can't recall. I gave away my other 920s, but decided to keep a yellow one that I repaired without its gasket. If I look at the phone from a certain angle, I'll see the light from the bottom keys, but it's hardly an issue for me. If you want the gasket and want to make sure you do everything properly from top to bottom, I say go with something that has the gasket, whichever it may be. That way, should anything happen to the old gasket, you won't have to go out and order something new. One of the most painful parts of this process can be the wait times for shipping.
Also, whichever screen you do end up getting, one common mistake some people make is leaving a protective film on the inner side of the digitizer screen, which will give the installed screen a rainbow effect. Some people think it's a defective or fake screen as a result. Just be careful that you take off the plastic films from both sides.
At the end of the day, I found that it's actually harder to find a bad screen than a good screen, so you have a lot of viable options. Pick out the one that you feel most comfortable with.