Sounds like you do not need to create another Ecwid account.
If you would like to have one store to be displayed without any changes on several domains simultaneously - this is possible with one Ecwid account (it does not matter, if this account is free or paid). Each Ecwid store can be mirrored on many sites at the same time and managed from one place. In other words, every merchant can have multiple storefronts in different places in the web. All you need to do is just to add Ecwid integration code with the same Store ID to the second site.
Moreover - you can even have different sets of products on different storefronts, that belong to the same Ecwid store, since this is possible by setting different categories for different storefronts. This way you will be able to manage inventory, customers, sales and other store data from one place, and the store will have the same merchant accounts, the same tax settings, the same e-mail notifications for these storefronts. Please refer to this article in our knowledge base for the details:
You actually need one more Ecwid account only if you need several independent Ecwid stores with different products sets, different merchant accounts, etc. you need to create an account for each of them.