The only difference will be the story up until you save Sandra in the Rescue.

That's it, it's all the same from there, aside from different dialog choices throughout the game, which I think is all smoke and mirrors and has no effect.

Honestly I was really disappointed how this was handled, the backstory you pick meaning so little

For example as a Street Kid I could have started with more Street Cred than the other backgrounds, earned it faster or had access to unique characters like say a fence or a bookie. Corpos could have started with more money and a nice car and have access to unique tech. Nomads could have been able to make more modifications to vehicles and unique weapons or whatever. Lots of possibilities. In a sense CDPR handled this like Night City itself. It's a facade, a hologram if you will. Looks real, but your hand passes right through it.

I use too many metaphors I think