Best use of workflowgen from another website


I use workflowgen from another website with iframe and workflowgen urls to create new request, launch action…

I would like to know what is the best way to use workflowgen outside the wfg portal.
In my website, I need to display all todo/ inprogress request with data summary for each user, I actually use workflowgen api with xml data.
Is there another way to do this ? to have json data at least. Maybe webhooks will be an option ?
I don’t really understand what is webhook or graphql ?

Another point, I would like to validate some action without open wfg forms. Is it possible ?
Is it possible to assign more than 1 request in the same method ?

Thank you.