Caching isn't strictly needed for most simple reads and writes (most of the errors are not critical) - but it can't do every action that an OS would expect a drive to handle like that. Especially any operations that involve editing or opening for write+read are pretty limited without caching. For full compatibility with all operations you will need
That does have some small downsides in the sense that all writes first get written to the local disk before being uploaded - but that's a fairly small price to pay. If you upload a lot every day you might want to put the VFS cache directory on a HDD rather than an SSD to avoid unnecessary wear (although that is becoming less and less of an issue on modern SSDs).
If you did your transfers in the command-line then there is no need to write-cache as you don't have to deal with OS compatibility - so if you need to move large amounts of files in bulk then keep that in mind. If it's not a lot of data then using the mount is fine for the convenience of it.
I would definitely use an empty directory for the cache to avoid any confusion, but I don't think it is strictly required.
One last thing. Usually moving around files on a drive can be done by just telling the server to move the file (rather than downloading it and re-uploading it). This is obviously a lot faster and more efficient and it can be done on a mount. However - rclone might not be able to recognize that it can do this when the trash and the drive are separate mounts, and I don't think there is a good way to put both together in the same mount.
So in short: If there are many large files - you may want to do that in the command-line as you can leverage server-side moves and avoid any bandwidth limitations.
Maybe someone else knows of a good way to work around this on mounts. I just don't access to trash very often outside of emergency recovery so I haven't looked into it much.