I found an av1-labeled version of a TV show on Sonarr, so I downloaded it, replacing my previous 264 version. I started to play it and realized it was a smaller 264 version.
Is there a way for Sonarr and Radarr to verify if a download's version matches it's label? Do I just need to stick with trusted distribution groups?
You can try to faff around with keywords and tags, e.g. give x264 or x265 a higher score rating, etc...
As a failsafe you can configure a trashcan location and specify that all deleted files go there first and don't get emptied for X amount of days.
Mislabeled files, not so much. Since there isn't really a way to verify the content until it's downloaded.
You can adjust things like which file sizes are considered a certain quality, e.g. HD or 4k. But one approach could be that you define tags for release groups which you know and trust. And give those tags a higher score. This should lead to releases by those groups being preferred.
You can of course add multiple tags with positive and negative scores. For example I use tags to give a higher score to releases that have 5.1 audio, or which are non-hdr.
Qbittorrent has a feature to execute a command on torrent complete iirc. You might be able to write a few ffmpeg commands to verify and delete/move/whatever based on that result. Not very user-friendly though ofc and requires some bash knowledge.