I believe that I’ve already answered your support ticket but just in case this helps anybody -
Firstly, to help with the loading (and in general good practice) you’ll want to make sure that your experience is optimised. We recommend keeping projects to around 5MB for best results. It’s often helpful to stream your videos if you are able to, however, this guide should help if that is not possible.
As for the sound not playing on load - for security reasons, browsers often require the user to interact with the experience before things such as audio can be played. The standard ‘Launch’ button we provide for WebAR experiences usually does the trick, however, since we cannot control the browser there is potential for this to be hit and miss. Because of that, you might find this post helpful as it links out to a couple of guides showing how our amazing users solved this sort of problem.
Have a great day!