The basic metrics for a landing page include:
'Bounce Rate' (which can be higher than usual if all you want is an email signup on the landing page itself and nothing more)
'Avg. Time on Page' - your design and content needs to keep them there long enough to lead to a conversion
'Pages Viewed per Visit' - not applicable if you have a one-page site
'Referring Sources' - provides invaluable insight into how people are finding your page.
The goal you have created is of course the most direct measurement of whether people are doing what you want them to do; set a goal for the conversion rate, at say, 2%, and then yes, by all means, A/B test multiple landing pages with different copy, with different email signup locations, etc. to see what your particular users engage with the most. How (with what external links) people are finding your landing page will impact the ease in which you can create multiple landing pages, and the multiple links needed to direct people to each.
Just be sure this page clearly spells out the benefits to the user of entering their email address and giving up personal information...