Daniel Steiner explained how the first street grid in NYC was laid out in Gravesend, Brooklyn, 150 years before Manhattan.

Area is measured in square units. On a centimetre grid each square measures 1 cm by 1 cm. Each square has an area of one square centimetre, 1 cm². The area of the square is the side-length ...

Overall, we highly suggest looking at real cities to get an idea of what your grid can look like. You don't have to stick with square grids everywhere, especially if you want some density variation.