Install awscli on Ubuntu 18.04 – Step-by-Step Guide

kali-rolling is the current active repository since the release of Kali 2016.1. The following entries should be in sources.list:

deb http://http.kali.org/kali kali-rolling main contrib non-free
# For source package access, uncomment the following line
# deb-src http://http.kali.org/kali kali-rolling main contrib non-free

This is answered well in snapcraft's official documentation.

In the interest of time, here is the pertinent portion:

Classic confinement is effectively un-confining the applications inside a snap. Applications which use classic confinement have the same full system access as traditionally packaged applications. Classic confinement is intended as a stop-gap measure to enable developers to publish applications which need more access than the current set of interfaces enable. Over time, as more interfaces are developed, snap publishers can migrate away from classic confinement to strict.

Classically confined snaps must be reviewed by the snap store reviewers team before they can be published in the stable channel. Snaps which use classic confinement may be rejected if they don’t meet the requirements.

Users should not attempt to override a strictly confined snap to make it ‘classic’ as this undoes the confinement and interfaces defined by the developer. In addition applications published as strict snaps may misbehave when installed with the ‘–classic’ switch.

As for a recommendation, you'll need to weigh the risks in your own mind. Consider the publisher of the software, their reputation/recognition and the fact that classic confinement snaps are reviewed before being published. Classic confinement is not all that different than having done a traditional apt install in terms of the access it allows to the program.