Couple of important notes:
Regarding the Belkin charger, the one they introduced supporting USB-C PD around the time of the first Pixels is
NON-COMPLIANT and potentially dangerous, to the point Belkin actually acknowledged the issue and offered refunds / other-model replacements. I don't know if the ones available online are updated and fixed or not, but even if so, I'd be hesitant to buy from any 3rd party to avoid getting the old stock (again presuming the item was updated to be compliant). What did non-compliant mean? What I noticed was that with the ignition off and the phone connected, it would actually actively discharge the phone dumping power into the outlet (PD can operate 2-way) potentially damaging the car's electrical system, and in violation of the spec.
Regarding other chargers that are 'QC' or 'PowerIQ,' etc... Pixels won't charge at truly high speeds with those, as they aren't running under the Qualcomm QC specifications.
The one I've been using the past few months indicates it is PD-compliant, and seems to be operating at the full rapid-speed, with none of the quirky discharge issues from Belkin, but I can't say with authority if it is fully compliant or not. It doesn't support all of the PD charging voltage combos, but does support the 2A/9V peak one used on the Pixel ('16) and is inexpensive, with a regular USB-out as well.
https://www.amazon.com/gp/product/B0747669PT/?tag=hawk-future-20&ascsubtag=UUacUvbUpU6015528