Looks like you will have to restore an image somewhere if you want to see what's inside it.
Seems so. Kind of annoying.
Here's a comparison of partclone (.pcl; mounting issues), dd (.img; size), and dd + gzip (.img.gz; some mounting issue and moderate size):
Partclone does have a significant size advantage. If only I could easily mount it. Comments suggest it may be possible, and I did install the partclone-util tool, but the documentation is sparse and I have not succeeded in mounting a "special image format".