Editing the subscribe form functionality so it only shows a specific subscription

I’m planning to sell some WordPress Child Themes and this membership plugin looks to be a good fit. Instead of “subscribe”, the button would say “purchase” because I want users to sign up for a membership and then download the theme. This way I can keep all the users separated into different membership groups, based on the theme name, making it easy to track who has which theme. I see many other benefits later on based on this setup. A couple of questions…

1. Is it possible to make edits to the subscribe form shortcode? Basically, I need more than 1 shortcode because I don’t want all the different subscriptions showing all on the same page at one time. Theme #1 should only have that theme’s subscription/purchase button. I’m envisioning a shortcode such as [subscriptionform id=”1″] or [subscriptionform id=”subscription_name”].

2. Is it possible to edit/remove the text on the form that says the following:

Step 2. Select a subscription

Please select a subscription from the options below.

Thanks in advance