Quick and simple...
Quick Charge 1.0, 2.0, and 3.0 do not quick charge the Pixels. They will charge fairly quickly, but not nearly as fast as a compliant PD charger. The newly announced QC4.0 does support PD, so chargers introduced with it should so long as they have the 9v2A charging profile. Similarly, make sure any PD charger you find supports 9v2A (not all do - for example, the Anker PD power bank doesn't, while the RavPower does).
I wish Google had enabled the QC4.0 profile (well, I can't say for sure they didn't, but there's been no indications) as that would allow for optimized charging to the degree earlier QC compliancies afforded, in addition to PD.