Recommended approach for mounting an encrypted remote using rclone on Windows 10 to be used by another program for syncing, like syncthings

should work. tho you need to test it for yourself.

have you searched the forum for freefilesync as that has been discussed a number for times.

for example,
https://forum.rclone.org/t/copying-vfs-cache-on-windows-10/31467/14

https://forum.rclone.org/t/how-to-resume-upload/8354/14