Flight deal services?

Ever since I moved to a place with an airport nearby, I've been wondering about those flight deal sites -- the ones like Scott's Cheap Flights, Mighty Travels, Thrifty Traveler, Faredrop, Secret Flying, Dollar Flight Club, etc (those are just the ones I found off a Reddit thread on r/TravelHacks).
Has anyone here had any experience with these paid services?

Also, does anyone know of a way I can search for a start and end point, and find other airports nearby to fly out of for much cheaper? I remember having used such a site earlier but cannot for the life of me remember its name now :-(