I can't help you on the USB-C packs, as I'm holding off on going to USB-C for another year or so, but I have one of the Anker 26,800 mAh packs, but it has dual USB INPUTS so charging time is much more reasonable when you pair it with one of Anker's multiport chargers. Even though my phones support QC, I went with the non-QC pack for efficiency reasons. If I'm running on battery, it's because 110v/230v isn't available, so I'll gladly take slower charging for more overall usable mAh. After Hurricane Irma, I was very happy with this decision since we were without power for 4+ days and someone tried stealing our generator on the 2nd night. It also is still better for battery health to charge them slower.

I'm not sure how old your battery pack is, but it shouldn't take 24 hours to put 16,700mAh into it. I'd suggest getting a quality cable and quality USB charger which can put out at least 2A per port. Figure 16,700/2000 = 8.4 hours, not including inefficiencies, so ~10 hours for a full charge. Using a Quick Charge charger won't make a difference unless your battery pack has the QC chipset built into it.

BTW, iPhones still don't support QC Quick Charging.