Triflexia is Comfortis with heartworm protection added, so only one pill with two products. If you already have heartworm prevention then go with Comfortis.
DE will help in pet bed areas and carpet, but once we got the Comfortis I vacumed at least every 3 days for while, washed and dried our bedding on hot every three days for a week and they were gone the next week. In fact, we joked that we should tell the dog to sleep on our bed so all the fleas would bite the dog and die- either that or take it ourselves. Lol.
I had moved from out of state and gotten our dog shots at a clinic so I didn't have a vet to call, so I ordered from New Zealand/Australia. You can also divide the large pills. I bought the large pills (for large dog) and learned I can divide them to the exact dose for our small dog and that saves a LOT of money.
