The Elgato Thunderbolt™ 3 Dock and Elgato Thunderbolt 2 Dock are similar, but there are some important differences:
Types of Thunderbolt Ports
Elgato Thunderbolt 3 Dock has two Thunderbolt™ 3 (USB-C) ports, while the original Elgato Thunderbolt 2 Dock has two Thunderbolt™ 2 ports.
For both Docks, you will have one free Thunderbolt port, since the other of the two ports will be connected to your computer.
Both Elgato Thunderbolt 3 Dock and Elgato Thunderbolt 2 Dock can deal with 4K video.
Elgato Thunderbolt 3 Dock can also use 5K video in certain circumstances.
See this article for more about 4K and 5K video, and Elgato Thunderbolt 3 Dock:
Can Elgato Thunderbolt™ 3 Dock use 4K or 5K displays?
See this article for more about 4K video and Elgato Thunderbolt 2 Dock:
Can Elgato Thunderbolt™ 2 Dock use 4K displays?
You can connect your 2016 MacBook Pro to Elgato Thunderbolt 3 Dock via a Thunderbolt™ 3 (USB-C) cable, and charge your computer.
You cannot charge any computer using Elgato Thunderbolt 2 Dock.