Is there a way to create a lot of product templates all at one time?

Yes and no.  We do have a tool called Quick Product Create that has a default set of 20 products with a simple logo template with default image areas.  You can find instructions for that here - https://help.zazzle.com/hc/en-us/articles/221630348-Quick-Product-Create

But, if you want additional products (we have thousands of options), you will need to create additional product templates one at a time.