Help with understanding Assets, specifically Quantity and Units

I’m trying to get my head around asset creation and the use of Quantity and Units in relation to Main and Sub Assets. I get that a unique asset is a single item, so quantity and units do not apply. I think I understand what the quantity and unit’s options do just not when/why you would use them.

For example

Question 1) If I am creating an umbrella asset for let’s say a design company, I could create a new Main Asset for 500RVN – what would be the pros and cons of altering the quantity and units of the Main asset?

Question 2) If I create sub assets for different portfolios of design work for 100RVN – what would be the pros and cons of altering the quantity and units of the sub asset?

Question 3) if you want to tie physical (or digital) items to assets do they have to be a unique asset or can it be a sub or main asset? I get that it greatly reduces costs to create unique assets if you have a lot of them in the portfolio but lets say you wanted to sell a car in the real world, you could just create a main asset and use that?

Theoretical examples or real-world ones for things people have already setup very welcome