i am planning to order a plugin from developer in future

i am selling shoes only and shoes have SIZES

in future i want to create barcodes based on product id and I would like to show to people the current quantity of stock. also there will be product purchases, so when there are some stocks coming it has to add certain quantity to the product by size.

for example, there is Product 1 with size XS | S | M . in my warehouse i will accept product 1 with quantity per each size: XS-200, S-400, M-150. how will i tell that i accepted this kind of quantity to update it automatically? for example by clicking purchase received... or lost or smth else. i mean how the plugin will understand the quantity for each size?

so my question is that how do i have to create products for best tracking inventory experience?

version 1. just create simple product and create size attribute (but i think each size will not be like a separate product and will not have an product id)

version 2. create simple product and then create size attributes and associate the sizes with products (in this case i think each size will have a product id)?

version 3. create group product and then add simple products (i will create one product per size)

i mean if I create just product attributes won't I have problems with tracking inventory in future and displaying it to people?

any ideas? which way is the best in this case?

Please advice

thanks