When I run tests I like to only change one variable at a time I might not understand enough about how you are defining the "creative" vs "unique promise" but if you are changing the scenery and the wording of the VSL you might have a hard time finding what works If you are just changing the messaging and keeping the rest the same than you just want to measure the results of each one and see what is working better. 5 pieces of creative might not be enough to truly get a picture depends on how much you are spending. If you aren't using ad groups in google ads I would recommend splitting your creative up into ad groups with keywords specifically for that ad group so if someone searches a specific term they will click on the ad that is related to what they searched. That will improve your conversion rate. Hopefully that helps