Deciding which field should be on Product node and which on product variations I'm wondering if I'm implementing my products the right way.

As I understand it should be the following.

I have different product variations with each their specific fields and SKU.
For example storage = 8 GB or 16GB

Then I have the main product to which these variations belong with main attributes such as the product name or compatibility. These are shared over the different variations.

So I consider I have my product nodes (or product displays?) with al my product information that is the same over the variations.
And I have my product variations with the SKU's and fields that are specific to each variation of the main product.

For me personally I think this is the correct way because you don't have duplicate data in your database. And if some field data needs to change, if it's a product specific field and not variation specific, you don't need to edit it over all the variation entities.

But I'm not sure that this is the correct way to do this according to standards, advise, other things I'm missing, ... . Because I'm very new to drupal commerce.
I think you're on the right track. If I'm not mistaken, a product display could be something like "Tee Shirt". The product variants would then be something like color or size. It's the same product with the core information, but the variants would be what ever is different, be it storage size or any other kind of variation from the original. 

Edit: The product display can display any products. The variants are dependent on the actual product but the display can show anything.