No, the use of VWO does not have a negative impact on your website ranking. For A/B and Multivariate tests, both the control and variations run on the same URL and test changes are made by VWO on the fly. There is no scope for content duplication, which otherwise can affect your SEO ranking.
However, SEO issues may crop up when you are running a Split URL test. To avoid the issue, use query parameter rel=”canonical” in the variation URL to avoid duplicating content. For example, there are two pages in your Split URL test (say, http://vwo.com/A.php and http://vwo.com/B.php). Whenever visitors land on http://vwo.com/A.php, half of them are redirected to http://vwo.com/B.php, which contains duplicate content.
In such a scenario where you don’t want B.php to affect your SEO, avoid content duplication. To do so, add the following code to B.php, that is, the noncanonical page:
<link rel="canonical" href="http://vwo.com/A.php" />
While Google will index both the pages, by adding the above code, you are telling Google to use only http://example.com/A.php for SEO purposes. Here’s the Google link on using canonical URLs.
To learn about the best practices for creating and running tests on your website with respect to Google Search, refer to this.