Yes, AV1 does save significant bandwidth compared to H.264 (roughly 30-50% better efficiency at the same quality). However, the compatibility isn't great yet, though it's improving as more devices/browsers add support.
The hardware requirements for AV1 encoding are actually much higher than H.264. You'll need either substantial CPU power or newer GPUs with AV1 hardware encoding support to transcode efficiently.

Support for AV1 in vimm-core is planned, but it's not a priority right now given the larger scope of the project.