I use the mergerfs so I can use hard links instead of having Sonarr/Radarr copy which creates the double space and IO when files get completed.
Is that to avoid slowness, or is there another motivation behind avoiding IO?
I don’t think you can use a filter with a mount as it just makes everything available.
There seems to be something that allows filters on a mount. The documentation says:
Note that all the rclone filters can be used to select a subset of the files to be visible in the mount.
Even with the cache setup, it really should not be 30-60 seconds though as that seems a bit off. What’s your mount command you are using?
I’ve started another thread so as not to derail this one. 30s - 60s play start time using a cache mount and plex. It has all the details of my setup.