I do not know which is the best approach in terms of database modeling. I have 3 kind of entities "Shipping Costs", "Billing costs", "Order costs" with different columns and different primary keys but they have in common that every entity could have one or more lines (detailed costs). I have modeled every entity with his respective "XXX_line" table (option 2) but lines had the same columns and are the same entity.
For that reason my colleague propose me the first option but I do not know how to model that in postgres (probably need an intermedite table?).
Thanks for your time.