I have a D700 (12mp) that I bought just after it was released. I still use this camera and I have made many large prints (up to 24”x36”). They all look great.
My current camera is 40mp and affords me the ability to crop heavily and pay a premium for storage space.
If I made 18”x24” prints of the same shot from both cameras, it’s likely no one would be able to tell the difference.
The only way to develop a true understanding of and appreciation for the genre is to study some of the greats.
List of Street Photographers