custom mailchimp form using HTTP API

I have a simple input type="email" that I want to use to create a subscription form for mailchimp newsletter. I will use the HTTP API and no plugin, this because I think this will be less overkill for the app. I have only two minor question about this implementation:

1) I need to pass to my plugin or function file the wp_ajax_nopriv and wp_ajax_ actions as normally I do with forms to manage the data right?

2) How I can manage the unsubscribe action from the user? I need to setup a link or something similar that will rely on a dedicated url qith action as param?