I use cells with safety circuits ("protected" cells) unless I have an application-specific reason not to, such as those where the typically extra length involved is a problem, etc. That is my baseline policy aside from such specific exceptions. I also ensure that all the various specifications for any cell are appropriate for my application(s) [such as max. continuous current, etc.]
The additional length, certain appearance details, etc. can often indicate that a cell is thusly equipped, although I rely on the manufacturer's / supplier's specifications as the definitive answer, as with all specifications. In the end, it is their specs that matter, not my conclusion based on observations, and if I don't trust their specs I don't buy their products in the first place. If the specs don't say it's "protected", then as far as I'm concerned, it isn't.
Yes, many flashlight manufacturers who include cells with a light do include "protected" cells in that case - in fact most / all of the reputable ones whose products I buy. Fenix, Streamlight, Surefire, and others are examples.
I buy cells from established, reputable, reliable U.S. distributors who also provide complete specs for those - which I won't name here because I don't think that's appropriate.
I've had good results with the Fenix-branded cells that they sell (also available from the various distributors referred to above), and that specifically includes 18650s, which they sell several variants of.
EDIT: BTW - In product / systems engineering where I work, users' common sense and good engineering practices for safety and reliability are not considered mutually exclusive. It is not an 'either / or' proposition. 'Both' is the preferred choice whenever possible. The human is often the least reliable element in a system, and ALL humans are prone to error. Furthermore, where safety is a critical objective, one safety measure is rarely considered adequate where two are practical. This also applies in 'high reliability' engineering, but particularly where safety is a concern.