Hi @henrybag,
Thanks for reaching out.
The Autoplay option is not available in the Embed mode. I would suggest you use the following code store into the ACF and use the Raw Content element to autoplay the Vimeo video.
<iframe id="vimeo_player" src="https://player.vimeo.com/video/257992348?autoplay=1&loop=1&autopause=0" width="500" height="281" frameborder="0" webkitallowfullscreen mozallowfullscreen allowfullscreen></iframe>
I have used the above video in my local environment and it worked. Please remember the above video is a sample video used for the example purpose, you need to change the Video ID to get your video to play.
Hope it helps.
Thanks