Yes. Background-video acceleration for plain HTML <video> tags is available on the Growth and Pro plans. See plans and pricing.
Enable it through the WordPress plugin or your manual SmartVideo snippet. The setting applies to eligible foreground <video> tags too, not just backgrounds. To keep acceleration on but skip one video, add class="swarm-exclude" to its <video> tag; see How do I exclude a video from SmartVideo?.
Your page or theme must set the background video’s playback attributes: autoplay, muted, loop, and playsinline, with controls omitted to hide native controls. SmartVideo scans for an MP4 source rather than detecting the video’s position or styling.
Follow How to accelerate background videos with SmartVideo for setup steps.