In AutoCAD, what is the best way to set up repetitive architectural building plans in terms of using single or multiple drawing files and block?

I am drawing up a complex of various apartment blocks with approximately 120 units of 6 unit types in total.The units are laid out over three storeys in 4 fairly similar apartment blocks, that are then arranged on the site around a communal garden space.The design is ideal for repeating drawing elements, but I am not sure the best way to go about this.There seem to be two extremes in the way I can set out my drawings:1. I could draw everything in one drawing, and simply define the repetitive units as AutoCAD blocks.2. I could set up a series of nested xrefs. Each of the 6 units types could a separate drawing. These could then be xrefed into 4 separate apartment block drawings. The apartment blocks could then be xrefed into a site layout plan.The first option seems the easiest, but I worry about the size and complexity of the file.The second option seems complex to keep track of all the external drawings, especially as they become nested. It is also complex to supply the .dwg files to the engineer and other professional consultants.

In Auto-cad there are 2 methods to do it.

1.for repetitive building plans convert them into blocks & use  for single of multiple drawings.

2.Xref is another method for repetitive building plans in Auto-cad..