how to connect 2 monitors to 2017 mac pro

I would personally stay away from the ones directly connected for a number of reasons, accidental damage being the main one. The only other thing to be aware of (Although shouldn't be a huge issue) is I don't think 4K 60hz can be dually driven from the same port, I think that requires using 1 on each side. You may be seeing some docks don't support multiple monitors and it'll be because they can't support the bandwidth to drive them over a single cable. That's a bit long winded but I hope explains a few things for you to better understand.

Looking at that dock, you'll need 1 USB-C -> HDMI cable (Or adapter as I mentioned, depending on your wants), and 1 DisplayPort to HDMI (DP/HDMI are the same thing, except DP was made for PCs and doesn't carry audio, HDMI was made for TVs HDMI lacks port retention grips). Whereas if you got a USB-C -> HDMI adapter, it effectively turns the USB-C port into a female HDMI port, allowing you to use any HDMI cable to make the connection. So if you get a USB-C -> HDMI cable, you'd need to use this all the time. What an adapter gives you is the option of using a straight forward solution. So you don't need a dongle or adapter, you just need cables. So that may lead to some confusion as a lot is marketed the same way but different specs. A USB-C dock might not have enough bandwidth to put all those signals through a single port, whereas TB3 does.

TB3 is vastly quicker than standard USB-C, and therefore there is a lot more you can do with it. The other thing to bear in mind is the channel bandwidth, Thunderbolt 3 is not the same as USB-C, they just use the same connector. But this is good, as it's not something you could do before. Eventually more things will be USB-C on both ends, but for now you need cables to switch signals in order to connect to the various ports. So what this means is you can use USB-C for pretty much anything, whereas HDMI can only be used for Audio/Video/DRM. It is a truly 'Universal Serial Bus', however most tech is still using dedicated ports such as HDMI. Alright so basically USB-C is a multi-port technology, meaning it is not channel restrictive like Ethernet/USB/Video/Audio etc.

How to connect 2 monitors to 2017 mac pro