Are all USB C ports equal?

Yes, its true! The left side ports data rate is different than the right on the 13” models only, The 15” models appear to be the same! I’m not sure what is different within the PCH between these to explain this as both use the same PCH. The late 2018 & 2019 models use a different PCH so it makes sense they are OK!

Late-2016 MacBook Pro models vary slightly in the data speeds they provide to each Thunderbolt 3 port.

• 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.
• MacBook Pro (15-inch, Late 2016) delivers full Thunderbolt 3 performance on all four ports.

The power input or output is the same across either side. in both the 2016, 2017, 2018 & 2019 models.

References:

Thunderbolt 3 Ports on Right Side of 13-Inch MacBook Pro Have Reduced PCI Express Bandwidth

Adapters for the Thunderbolt 3 (USB-C) or USB-C port on your Mac or iPad Pro