Thank you for contacting us! Sorry for the delayed reply. We aim to reply within 24 hours of being contacted, and we’ve been getting caught up from over the long holiday weekend.
Please note that we’ve received your direct email as well.
You’d mentioned seeing our video with a 2019 MacBook Pro 15" and 4 displays, your 2018 MacBook Pro 15" can also support four displays via Thunderbolt 3 using the same products we used in our video. (https://www.youtube.com/watch?v=VGdvtQS0Cp8)
Your system specifications for your reference: https://support.apple.com/kb/SP776?viewlocale=en_US&locale=en_US
Dual adapter: http://plugable.com/products/tbt3-dp2x-83 or https://plugable.com/products/tbt3-hdmi2x-83 (depending on if you prefer DP or HDMI)
You can connect our dock to one side of the laptop, and you can connect our dual Thunderbolt 3 adapter to the other side. They cannot both be connected to one side due to Thunderbolt 3 technology limitations.
The dock offers one native DisplayPort output and comes with an active DP to HDMI adapter. To connect a second display to the dock you would need to use a USB-C to DP or HDMI adapter/adapter cable (connected to the second downstream Thunderbolt 3 port on the dock).
USB-C to DP cable: http://plugable.com/products/usbc-dp or http://plugable.com/products/usbc-hdmi-cable
We’re unable to make specific recommendations for monitors, but the monitors linked to should be compatible. You’ll just need to make sure to have the appropriate cables/adapters to physically connect them.
Thanks and best wishes!