SKU Struggles

I am looking to create a proper SKU system for my store. I have an Etsy store and Shopify store so having the inventory linked is kind of important. I am running into some problems:

I have options like this:

1 Liter bag

3 Liter bag

Is there a way to make an SKU that removes 3 inventory when the 3 Liter bag is selected?

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I have for example a listing that is 3 plants with the following 4 options:

Plant A

Plant B

Plant C

One of each

Is there a way to make inventory match this type of listing? So it actually knows there are 2 A plants, 3 B plants and 5 C so it can offer that and 2 of "One of each"?

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If anyone has a solution I will compensate you in any way possible! I can review your store or give you feedback on something you would like. (Or send you a free plant!)