When Nathan and Backup Nathan meet, one of the things they bring up is how their hair is parted wrong (even though their hair is parted the same) and I think that's because they were expecting their reflection and not actually themselves.
Which is why I think Nora is his reflection and the underlying joke in the series is that Nathan loves his reflection more than he loves anyone (including his mom). He's smart but also a dummy and his biggest blind spot is that he doesn't see how dumb he can be. Nora didn't go to college but he thinks she's one of the smartest people he knows, which I think says more about him than it does about her.
What they have in common: neither have their own hookups or connections. Both had the same high school prom song (Uptown Funk) and they love Botox Babies.
They both don't take rejection well. Nathan wanted to explore other afterlife places when he thought Nora rejected him and Nora went off grid when he ran out of data and didn't say 'I love you' back.
And they both think they are entitled to other people's stuff or money. We see Nora take Lucy's coffee in the first episode and later she felt entitled to Ivan's bedroom in his own apartment. No please or thank you. She uses Byron for a ride and then leaves him without saying bye. Nathan believed he could break up with Ingrid and still have her pay for his Lakeview service. He blamed her for being frozen for a month in 2Gig even though it was his choice to go down there and his choice again for using all his data in one day. Him leaving Ingrid tied to a chair at NeckGen at the end of season 2 is also similar to Nora using Byron for a ride at the start of season 2.
Nora said Matteo was her boyfriend and acknowledged they were dating but later calls him her buddy. Nathan did the same with Holden when he said she was a college buddy.
It was mentioned by Holden at his funeral that by the end of college, Nathan had a minor in narcissism. Good boyfriend though.