The NEC (or CEC) should be referred to for wire and breaker size. The code may require a different wire rating than the breaker supplying the circuit ( for ex., 15A wire and 20A breaker). The code changed the requirement for heating circuits in recent year
yes saftey is a concern with ALL heating devices
but you have your statement backwards
it is Against code to use a breaker that is larger rating than the wire can handle
you Can Use a breaker Smaller than the wire rating.. 15amp breaker on 12ga 20amp wire
NO UL rated poratble device will use more than 1500w aka 12.5amps at 120v
hardwired mounted heaters come in a variety sizes and ratings