you can setup groups in your echo app. just go to smarthome - groups.
That's not enough. I'd like to just say Alexa Party, or Alexa Trigger Party and have either Alexa or IFTTT change the lights, start a certain music station, turn on the AC, etc., all just with one command. I'm surprised IFTTT hasn't implemented an "AND" operator so that triggers can be strung together. Heck, with AND a single Alexa command could power up the world lol.
sorry but you can have a group of lights to turn on whether it is all in one room or all of them in the house. I have several groups set up, one because whenever the power goes off then comes back on, every single smart light is on and it is easy just to ask alexa to turn everything off.
as far as the car and garage door, it may or may not need ifttt depending how compatible it is with alexa to begin with. If setting up groups, and the device is in the setup list, then it may not need ifttt, just a group. It is something that person will have to play around with when they get the garage door opener unless someone here knows "for sure" since it is apparent you don't know and I sure don't.