I think I can definitely answer this question if anyone is still confused.
In Anandtech's Nexus 5X review they used 3 different chargers:
1) The included 15W (5V/3A) type C charger
2) A Chromebook Pixel 60W type C charger
3) A QC 2.0 certified 18W charger
All 3 charged the 5X from 0% to 100%...
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