Greetings Lindsay, and thanks so much for your question! You absolutely can edit the redirected page by adding multiple pages to your test.
So, when you are setting up the test (in the A/B workflow, the Experience Targeting workflow, or in Auto Target), type in the URL of the redirected page in one experience. In the other experience, click on Configure> Add Additional Pages. You will see a "+ Add Page" option appear in blue. Click on this, name the experience, and enter in the same URL of the redirected page here. Once you hit the blue Save button, you will see the redirected page load, and can make any edits from here. Users will be redirected to this edited version of your redirected page. For more on this topic, visit Adobe Target's Product Documentation on Multipage Activities
Hope this helps, and feel free to reach out here if you have any other questions!
Warmly,
Amelia