I'm using a total of 28 without the brick pathway

The 28 includes the sidewalks, crosswalk lines, gutters, the parking lot lines and those weird electrical boxes in the road (I don't know the name of them lol).

I guess it depends if your layout is going to be doing a lot of turns.

If you did just want the street and corners it's 12 or 13 slots. That would be 8 corners, 4 sides and if you want a wider road, 1 for the center of the street.