One site, several connections
Your business is one Camello site, even when its pages are served by more than one system: a WordPress site on example.com with a Shopify store on shop.example.com, for example. Each system is a connection on that site, and every change goes to the one that serves its page.
When to add a connection. When part of your business lives at another address or on another builder: a store on shop.example.com or at a Shopify address, or pages on a second builder. Not for a second business; that is another site (see Add another site).
How. In onboarding, under "Your site", answer "Does your store (or part of your site) live somewhere else?" with Yes, say what those pages run on and give their address. Later, on the site's Connections page, press Add a connection. A site can have three connections at most. Camello never adds one on its own: when the free check notices a second address, onboarding states it and asks you to confirm.
What each connection does. Camello reads the pages of every address you listed and sends each change to the system that serves that page. A change on a WordPress page goes through the plugin; a change on a Shopify product goes through the Shopify app; a change on Wix pages comes as copy-paste steps. When a site has more than one connection, each card says which: "On your Shopify store", "On your WordPress site", "On your Wix pages".
WordPress plus Shopify. Pages on example.com are WordPress's, so the plugin writes them. Products, collections and the store's own pages on shop.example.com are Shopify's, so the Shopify app writes them. Blog drafts go to the WordPress blog. Every change is one click, with Undo.
Wix plus Shopify. Store changes are one click through the Shopify app. Changes on the Wix pages come with Wix's steps and a Done by hand button, because Wix has nothing Camello can write through.
What gets skipped. Pages at an address no connection covers are not read, and no change is proposed for them. The Connections page says so and names the address, so you can add it if it is yours. A page on your own domain that no connection lists counts as part of the main site.
Shopify's Buy Button. If your products are sold through Shopify's Buy Button embedded in a WordPress site, the pages Camello can change are WordPress's. No Shopify connection is offered for that in this version, and onboarding says why.
Billing. One site, one plan, whatever its connections. There is no price per connection.
Removing one. A copy-paste connection is removed from the Connections page. A connected WordPress plugin or Shopify store is removed with its Disconnect button, and its pages stop being read.