I do not know what shopify e-com is also.
It's the primary Shopify e-commerce platform. Meaning selling items online. Whereas Shopify POS is the brick-and-mortar app that runs in a physical storefront. Shopify e-com has plenty of third party apps available, and Shopify POS is steadily growing its app catalog. While additional recurring subscription fees for these apps isn't exciting, if there are functional gaps in Shopify that you cannot workaround via business processes, via their API's, etc. then it is what it is :)