When you create the web form, you check the box "Send a double opt-in email when this form is submitted" When you check that box, you get a drop down list of any email template where you have included a double opt-in link. There's even a little line of explanation "Lists only email templates with default or custom double opt-in links".

When you add a contact to a follow-up sequence via an action connected to the double opt-in link,
then you have contacts going into that same follow-up sequence whenever you use that particular opt-in link. So once you use a particular double opt-in link with more than one web form, you give up a unique connection between the triggered follow-up sequence and any particular web form.

But if you don't care about creating different follow-up sequences, several forms can use the same double opt-in link, and the actions connected with that double opt-in link.

If you want to at least tag the contacts uniquely, depending on what form brought them in, you can do that vie the action set connected to the particular form.

One downside of this method is that you end up with one heck of a long list of double opt-in links.
Unlike web forms, there's no search field for double opt-in links.