If anyone has much simpler needs, I found a way to do a really simple text box popup with a title, subheading and basic text area by hacking the built in form. Don't use it on a page that needs forms.
In the page settings for the page you want to do this with put the following code:
<style>
.form-button-wrapper{display:none;}
form .field-element {display:none;}
</style>
Then create a form on your page, clear all the stock form fields and create one new simple text field, and in the advanced settings, set it to open in lightbox mode. The title and description of that field form the content of the popup