'fast charging' is about 0.5C charging which is within the maximum which is about 0.75C.
Shouldn't have any noticeable impact on battery life over anything else that affects battery life.
Also don't listen to people swear by 'have to do full discharges to save battery life' or really any other myths.
my not fast-charging iphone has shit battery life around when the 1 year warranty expired lol.
QC gotten better each iteration with power and efficiency.
Does nexus even use snapdragon QC though? Thought it was just normal usb-c.
It has fast charging whatever google created just for the 6P/5X. Which sucks cause trying to get 3rd party chargers or battery packs is a crapshoot.