How important is it to closely match the wattage of the power adapter that came with my Macbook if using a third-party replacement charger? What are the Pro's and Con's of supplying it more or less wattage than the factory charger?

Ask Apple Support.

I think you're going to have to ask Apple this question, as I can't find any specifications for this, nor any official answers.

In general, this should be okay. But some of the older USB-C stuff was a little... wonky.

The "fun" here is figuring out whether the device and the charger match, which isn't always entirely obvious, and Apple has posted very little detail on Mac chargers and USB-C requirements for the USB-C Mac models.

A USB-C charger that supports equal voltages and the required amperage or more than what the device requires is expected to be fine, and many USB-C chargers will offer the connected device a range of available voltages and amperages, and the device will then request appropriate and compatible power delivery. If the device doesn't like the choices, it won't play with the charger.

There's a chart of voltages and amperages here:

https://en.wikipedia.org/wiki/USB_hardware#USB_Power_Delivery

You can see what your Mac has negotiated here (I'm assuming this is where you're getting those values):

Identify your Mac power adapter - Apple Support

Related: some recent Macs also support fast charging (MBP 15" 2016 is not listed):

Fast charge your MacBook Air or MacBook Pro - Apple Support

I've been working on the following tip on this topic, which might provide some more background:

Apple USB-C power adapter volts, amps - Apple Community

When a charger doesn't support the expected voltage and wattage:

https://9to5mac.com/2021/01/04/making-sense-of-the-oddities-of-apples-usb-c-chargers/