Well I can tell you that it's this monitor:
This Certified Refurbished product is manufacturer refurbished, shows limited or no wear, and includes all original accessories plus a 90-day manufacturer warranty
www.amazon.com
which isn't actually made anymore, though the 24" is at the Apple Store. I got the 21" model for $300 at the time from New Egg refurbished. I'm driving it on my maxed out 2016 12" MacBook (m7, 512 GB HD).
This article mentions how it all works, though it is talking about the newer 24" monitor. However, this applies to the 21" model as well.
Learn about the 23.7-inch LG UltraFine 4K Display and how to use it with your Mac or iPad.
support.apple.com
I would note that the newer model actually has a lower pixels per inch count as it is a slightly lower resolution.
You don't need a dock at all. You just plug in the USB-C cord, and everything is golden. You have 3 USB 2.0 ports on the back which I use for AV 40 monitor speakers, my SM7B microphone, headphones, two other ports to plug in guitar/keyboard, my external backup hard drive, and whatever else I need for the last port.
But yeah since you're talking about 1 port at regular USB 3 speeds, USB 2 is basically what you would get on the back. I may have read somewhere of someone driving two monitors (in addition to the laptop screen), but that may not actually be possible.
Attached is my current setup. I'm also attaching a pic of my display mentioning 4k 60 so you all know I'm not making things up.