Up-to-date solution for cloning commerce product-variation types and their product displays
After trying out all above modules, I can clearly say for my usecase the winner is:
bundle_copy for cloning product displays in combination with bundle_copy_commerce for the product variations.
Cave: I didn't use the clone/copy feature of both moduls because of errors and poor cloning (fieldgroups weren't copied) – instead I used the export/import feature:


Export the entity
Replace in the code from step 1 all occurences of the bundle name with a new name
Import the code from step 2 again.
When using fieldgroups you have to make sure, you rename the fieldgroups in step 4 with a unique name (add the bundle name as a suffix, for example).