After you register as a Wave user, you can create up to 5 videos and export them up to 10 seconds long in SD quality. The videos will have the Wave watermark. Also, you will be able to upload only 2 video clips and 2 images (50 Mb in total), and 1 audio file.
Yes, you can use stock video clips, images, and audio files in your videos. All subscriptions have access to the Premium stock. However, there are certain limitations for the video format and its length for the free plan. There are several premium video clips included in the Agency and Ultimate plans (meaning that you won't have to purchase them separately). Upgrade to enjoy all the great features of Wave!
When you are ready to upgrade, please visit this page: https://www.animatron.com/wave/pricing to choose a plan that suits you best.