Thanks again for your response. I am certainly rethinking my whole setup at this point...
As to this point about file verification using hashes, and to get this completely clear: Despite crypt lacking support for file hash verification, does running cryptcheck after the upload has completed perform an equivalent verification of file integrity?
In fact, in this post (Integrity of rclone ENCRYPT - #5 by ncw), Nick says:
No, the crypt backend does a version of
rclone cryptcheckwhile it is uploading files so it should notice corruptions at that point.
Sorry to keep going on about it, I just want to get it clear. I thought RClone crypt was a really nice solution for storing potentially sensitive files on a variety of cloud backends, but you are now causing me to doubt this somewhat... 
If so, I will have to do a lot of re-thinking.