squashfs (which these loop devices contain) does not use any memory unless you actually access the data in it (i.e. by running a program which in turn loads libraries) …
when unused, the files in /snap are just mount points and nothing in there should occupy more ram than needed for holding the directory and file structure, when you do an ls or find command on it …
as long as you do not run the snap app itself, the only resource used is the disk space in /var/lib/snapd/snaps but no CPU or any significant amount of RAM.