Going through some old videos and have decided to use #Handbrake to re-encode for space reduction. On this one video, I reduced it from 181.3 MiB to only 38.4 MiB, about a 79% file size reduction! Wow!
The original file was an MP4 encoded with H.264 and AAC. I re-encoded the file to #Matroska using the #AV1 and #Opus codecs. Everything was based on Handbrake's Fast 1080p30 preset.
(EDIT: To further add, the original audio was at ~256 Kbps encoded in AAC).
For AV1, the rate factor was set to 30, the frame rate Same as Source, and the rate factor 30. For Opus, I set the bitrate to 64 Kbps.