Best practices and setting for mounting gdrive and s3 services for streaming with plex

welcome to the forum,

first, check out my summary of the two rclone caches.
https://forum.rclone.org/t/status-about-using-rclone-for-music-storage-playback-in-2021-access-times-improved/27648/34

does not matter that much, only applies when plex is scanning a library, not when streaming a media file.
i disable auto-scanning, and only manual scan when adding new media files.

try --daemon-wait=0 - that has been discussed in the forum.

for s3, i set --dir-cache-time=9999h and after adding files to the remote, i manually refresh the vfs dir cache.
to the mount command, add --rc --rc-no-auth
when i want to refresh the vfs dir cache, run rclone rc vfs/refresh recursive=true -vv

sometimes i use that, sometimes i do not.
most users use --vfs-cache-mode=full

that is up to you. how much space do you want rclone to use and how long do you want files to stay in the cache.