The most effective way I've found to disable autoplay is to simply block the video content networks which provide these. At my last update, it was a rather small set.

    0.0.0.0                 player.theplatform.com  # Autoplay video
    0.0.0.0                 link.theplatform.com    # Autoplay video
    0.0.0.0                 ci-2862d2c8d6-68f418d2.http.atlas.cdn.yimg.com # Autoplay video
    0.0.0.0                 big.assets.huffingtonpost.com # Autoplay video
    0.0.0.0                 ht1.cdn.turner.com      # Autoplay video
    0.0.0.0                 ht2.cdn.turner.com      # Autoplay video
    0.0.0.0                 ht3.cdn.turner.com      # Autoplay video
    0.0.0.0                 ht4.cdn.turner.com      # Autoplay video
    0.0.0.0                 ht5.cdn.turner.com      # Autoplay video
    0.0.0.0                 ht6.cdn.turner.com      # Autoplay video
    0.0.0.0                 ht7.cdn.turner.com      # Autoplay video
    0.0.0.0                 ht8.cdn.turner.com      # Autoplay video
    0.0.0.0                 ht9.cdn.turner.com      # Autoplay video

Alternatively, uMatrix should allow you to globally blacklist, then optionally whitelist same.