Are those ports on the MBP 2017 USB-C or Thunderbolt 3 or they can change depending on what cable or adapter you use?
The Thunderbolt 3 ports on the MBP are USB-C* connectors that can do Thunderbolt (20-40Gbs), USB 3.1g1 (5Gbps), USB 3.1g2 (10Gbps), DisplayPort (which can also drive HDMI adapters) and/or charge the computer depending on what you connect and what cable you use.
If you just want to connect a display, and have a free port, a USB-C to DisplayPort or USB-C to HDMI cable should do fine. Check the reviews, though, there are some rubbish ones around - also search MacRumors for recommendations.
If you want a hub/dock with a single cable connection to your laptop for display, charging + USB ports, ethernet, sound etc. then
roughly speaking:
* If its a "standard" res display (2560x1440 or less) then you can consider a cheaper "USB-C" (non-Thunderbolt) dock. However, be aware that everything apart from the display is sharing a single USB 3 connection (not all, if any, such hubs support USB 3.1g2)
and if you connect a 4k@60Hz display that degrades to a single USB
2 connection.
* If its a 4k display then you really want a Thunderbolt 3 dock like the Caldigit TS3+ (plus suitable cable) because only Thunderbolt can fit a 4k@60Hz DisplayPort signal
and high-speed data down a single cable. USB/ethernet performance should be better because the ports aren't all sharing the same USB 3 connection.
* If its a 5k display, then the LG/Apple 5k Thunderbolt display is the only game in town at the moment, and that includes a charger + a couple of USB-C ports (you'll need dongles). Note that the smaller
4k version isn't Thunderbolt so the ports are only USB 2 speed.
* Check to see if the hub/dock you're looking at supplies enough power for your MacBook Pro (esp. the 15" ones). You can probably live with slightly below-par power (it shouldn't damage anything) but your MBP might not charge, or even lose charge, while doing heavy work.
Also, either go and read the various articles on the types of USB-C and Thunderbolt cable (and despair) or make sure to connect each device with the cable that it came with...
*"USB-C" is a confusing term which could refer either to to just the connector, the connector + asscociated protocols for device/cable type detection and power delivery
or be used to distinguish a USB/displayport/power-only port from one that also supports Thunderbolt 3 (which always uses USB-C connectors)... and, yes, far from being "one cable to connect them all" there are multiple permutations of cable types - pick the wrong one and your device either won't work, will work very slowly or won't charge. Enjoy progress.
