Your start up time requirement might be met with an NVMe SSD running on PCIe 3.0x4.
Qubes relies heavily on a fast SSD, so try upgrade from SATA SSDs to NVMe SSDs.
Also there is some discussion on how to tune your SSD for ~1s improvement. Like 4kn SSD and 4kn template.
Regarding your video issue, that might be to blame the decoder in your template. Generally debian template has a better compatibility with videos.