Graph QL Create Products Best Practices, basic workflow

[CrazySquirrel]

Hello,
We have to create over 100K products.   We dont make use of any kind of product options (yet).  So for each product, we need basic information set like:

Handle

title
Description Html

sku

price

Image1

Image2

It is our understanding that we need to create a product, and one variant for each product.  Here is the workflow we are trying to use:

1. Call: productCreate mutation.  store the returned product Id for later.
2. Call ProductVariantsCreate mutation (known as productVariantsBulkCreate).  Pass in the product ID.

I have a few questions.  

1. Looking at your documentation for ProductVariantsCreate, it shows this json for the inputs:

{
  "productId": "gid://shopify/Product/20995642",
  "variants": [
    {
      "price": 15.99,
      "compareAtPrice": 19.99,
      "optionValues": [
        {
          "name": "Golden",
          "optionId": "gid://shopify/ProductOption/328272167"
        }
      ]
    }
  ]
}

My first question is about:

variants[0].optionValues[0].optionId

1. How are we passing in an ID here?  Where did that ID come from?  Is this required?  This example in your documentation uses a "Golden" option, with an option ID specified.  Im getting this back from your API:

"userErrors":[{"field":["variants","0"],"message":"You need to add option values for Title"}

So I assume this must be required.

2. My second question is: Is a default variant created anyway when I create a new product?  If so, then the process I am trying now would result in 2 variants (one real one and one bogus one).

Also, if you have any tutorial or best practices guide on how to do this, please give me the url.