There are many choices out there and everyone may have different requirements. That being said, I do believe that the Lowes Iris Plug is your best option for several reasons.
- It’s easily obtainable at your local Lowes store which also makes it easier to return if necessary
- It has both Zigbee and Z-Wave protocols thereby extending both meshes
- It will run locally (it will still work without Internet)
- They will also report energy usage
- You can purchase them relatively cheap with discounts
- There is a switch on the device itself for manual operation
- Very reliable so they rarely ever drop off the network
- Won’t block the top outlet if you use the bottom plug.
It is best to get some repeater devices because Smartthings can only handle up to 32 end devices such as your bulbs. I use my plugs for a coffee pot, fans, lights, and even my TV. If you can’t find a use for them, you will eventually. 
Right, no need for your lamps with smart bulbs.