I just had a look at the new LG UltraFine 4K monitor for Mac, looking at the box (image below) with the Mac logo, it seems likely that Apple were heavily involved in the design
A single USB-C cable (included) provides up to 60W of charging power to the MacBook Pro. And three downstream USB-C ports (480 Mbps) offer additional connectivity and power to compatible devices and accessories. There are no other ports.
The new Apple laptops come equipped with only Thunderbolt 3 (USB-C) ports, I suspect the whole industry will standardise on USB-C pretty soon but at the moment there is obviously the need to support legacy peripherals. Fortunately Apple have put together a page describing most of the adaptors that might be needed. This includes standard USB, HDMI, VGA and Lightening cables. Remember up to six devices can be daisy-chained to each Thunderbolt 3 port of the MacBook Pro; and the Thunderbolt 3 (USB-C) to Thunderbolt 2 adapter doesn't count as a device against that limit.
MacBook Pro (15-inch, Late 2016) delivers full Thunderbolt 3 performance on all four ports.
MacBook Pro (13-inch, Late 2016, Four Thunderbolt 3 Ports) supports Thunderbolt 3 at full performance using the two left-hand ports. The two right-hand ports deliver Thunderbolt 3 functionality, but have reduced PCI Express bandwidth.
MacBook Pro (13-inch, Late 2016, Two Thunderbolt 3 Ports) delivers full Thunderbolt 3 performance on both ports.
I needed to buy a new monitor and since Apple don’t supply one at the moment I spent a week searching through online reviews and then looking at a selection at various stores. Eventually decided to get the Dell P2715Q 27-Inch Ultra HD 4K LCD Monitor. Very happy with the selection I just hope Apple don’t announce a new monitor next week!
I should have noted that you have to buy a separate AmazonBasics High-Speed HDMI 2.0 Cable - 0.9m / 3 Feet (Latest Standard) Supports Ethernet, 3D, Audio Return . Also if you need a Mac compatible web cam, this one is highly regarded.