Does this product generate Fillable Forms, for example convert my existing word/google form to an electronic form fields embedded to a website, then input the data back into google doc/word doc?

Answer:

FormNX will help you create forms & also generate PDFs from the forms.
So based on your need it can generate PDF but by default it'll not fill the content in google doc. You can use some automation tools like Zapier/Pabbly/Activepieces etc to do fill the doc using the data of the form.