What line weight guide is ideal for different elements of an architectural plan in CAD softwares?

Answer 1

While lineweights are a highly subjective topic, a good starting point would be the (US) National CAD Standard, which includes the AIA Layer Guidelines that among prescribes lineweights (along with many other CAD standards such as CAD layer naming).

Here is a summary:

https://www.cadcam.org/blog/aia-layering-standards-cad-drawings/