I just got the smartthings v2 and bought a few GE smart switches and one smart plug.
I have a smart switch (on/off not dimmer) on my back door light and a smart plug (on/off not dimmer) on my back step lights.
I grouped the two in their own room, I would like to be able to click the wall switch and have it control both the light and the smart plug (obviously it already controls the light fine).
I use IFTTT to control multiple things with one button. I have my fireplace switch set to turn on my wemo maker to turn it on, and my smart outlet that controls the fan for the fireplace, all thru IFTTT.
You can use the Smart lighting smartapp to sync all the switches together. This is the easiest way and no delay. Also local processing if your are using the genetic ST device handlers.
IFTTT is great, I use it all the time, but you should not need it for this purpose. As @Navat604 mentions, you can do this with the official smart lighting app. The instructions are in a how to article in the community created wiki.
IFTTT might be a little more intuitive to set up for this, but it does add additional lag. How much varies from house to house. At my house it’s a pretty consistent eight seconds, which would be more then I personally would want for a light switch.
So as you noted, there are indeed many ways to do this with SmartThings. Whichever works for you is good.