Testing variables for video autoplay

I'm trying to test to see if having an auto play video helps more interaction with the video. Right now, I have a video on my website with a playlist of videos underneath it. Currently, the video needs to be clicked on to play the video and a lightbox pops up and they watch the video. I am not getting much interaction with the video player so I wanted to test a silent autoplay. I'm not sure that my lightbox player shows the number of video play-through, but I can see a heatmap and clickmap and it's pretty cold. I can set up a "b" page with autoplay and then set up an A/B test. However, I am at a loss on how to judge what works better. I can look at the heatmap, but what if people are just clicking on it to shut it off? What if I'm getting more views, but people aren't actually interacting with it, they are just leaving it playing while they view the page? I can test conversions to see if they buy the product, but how will I know if changing that one autoplay video is causing more people to buy the product? I have a A/B tester plug in for my site, but I'm fairly new to A/B testing.