Moving from plexdrive to rclone. plexdrive was (and for some still is) the best way of mounting your google drive for plex. But as rclone has improved and plexdrive is no longer being actively developed. I tend to use just rclone now.
In theory the best way I had found to migrate from plexdrive to rclone was just to un mount your plexdrive and mount your drive to the same location using rclone, that way plex sees the same paths to all your media
But after trying to help out on the plex forum, it seems that may not always be as simple as that, and you may need a slightly more complicated process… So if the easy option did not work then…
You will need to create a new mount point folder for rclone, and mount your drive to this new location. So you will have your google drive mounted twice, once by plexdrive and once by rclone on 2 different folders / locations.
At this point it would probably be worth using the symbolic links as detailed on the rclone page
Then in Plex, edit each of your libraries and add a second location that points to your new mount, or symlink if you set those up. Plex will then scan the new path and add the files it finds.
You will probably find that all your movies get shown with a 2 in the display, as it will now see 2 copies of the movies. Once the scan has completed you can edit the library and remove the path that points to plexdrive and empty the trash and those duplicates should disappear.
This is basically a summary of the info you can find here:
in the section: Moving Content to a New Location