On A 3-way, there’s an extra terminal, known as the “popular.” Power comes in to the switch around the popular, then two “traveler” wires connect the initial switch to the 2nd around the brass terminals. For the most part, smart light switches will work with any light — incandescent, LED, https://raymondutspj.amoblog.com/a-secret-weapon-for-electric-hub-56610634