USB-C Charging Speeds / Charger Outputs
A good Multimeter is fantastic - I use one all the time - however it's not clear from your question just how you're using a Multimeter to take your measurements? 

Considering we're talking about a fairly recent model MacBook Pro, I suspect you haven't opened it up to take these measurements. Instead, I recommend you download and install coconutBattery1. It provides a whole heap of information that you'll find useful, and from memory includes both Discharging and Charging measurements in watts!

Some thoughts

It's not clear from your question why you're investigating all this? Unless you've actually got a problem you're trying to address, using the charger that came with your MBP should be perfectly fine. Also, in relation to you not finding any articles that indicate what a normal USB PD output is relative to the devices they connect to, that's because PD stands for Power Delivery and most of these devices are just designed to allow the power travel through them from the charger to the device being charged. 

In other words, you can use a hub with a USB-C PD port with a 2017 MacBook Pro and also use it with a HP Elitebook and the voltage/watts will differ, depending on the device and charger.

1 I am not affiliated with coconutBattery in any way.