I’ll try to give a brief road-map and considerations
The WF API provides functionality to fetch collections and items and also to create them. This could be the simplest approach to your use-case.
In general – you will need a server or a third-party service to handle the communication between your clients- and your site. You can’t handle this logic inside your WF site, because you only can access the client side
(it might be possible to have this logic inside your page and have it executed on each visitors device, but that’s a horrible idea for a plethora of reasons).
To evaluate between creating your own custom solution and more easily implemented solutions from third-party-services, consider:
costs vs complexity
Services like zapier provide lots of “integrations” that are easy to create but impose limitations that can be difficult to work around and also can be quite costly. Creating your own server is vastly more complex, if you are not familiar with JS - especially with server frameworks or other backend languages/stacks BUT can be much more affordable and also vastly easier to scale and extend in functionality.
Status & metrics / tracking issues
Surveying and tracking issues could be difficult with 3rd parties (not sure, you have to check). Your own server can have all the metrics and handlers that keep you up to date.
Before you start anything, I’ll recommend to thoroughly check the following:
For any approach, get familiar with limits of either 3rd parties / WF API
3rd parties often limit rates and services that can be connected and explode sometimes in costs when for example having to set up 7 sites?
WF API seems to be quite rugged, however I’ve seen multiple topics on the forum with questions of weird/unexpected behavior and issues with the rate limits or unclear documentation. The github repo is also maintained poorly. Get informed about those things before proposing to clients. You surely don’t want to be in need of explanation if things don’t work as advertised!
I’d suggest starting to check the 3rd party approach! I’ve found that you can create CMS items (do you use eCommerce??? - check if this works too) via new rows inside Google Sheets! This might be handy!
If you can convince your clients to just fill in new products in a single sheet and have it updated automatically, the better.
Have a good look at several services and think how you can connect all those sites with yours, if you also can persuade them to get on to WF and leave WP behind, that’s a win on their side too!
Let me know how you progress