Yes I’m aware of the studies re: fast charging , and the importance of avoiding dwelling at high charge levels :)

If a device charged overnight does not support limiting charging to 80%, a 5W charger means the device spends less time between 80% and 100% versus a higher wattage charger.

For a newer device that does support limited charging to 80%, I agree that there’s probably a little difference in battery aging between different speed chargers, however for overnight charging, where I really don’t care how long it takes to charge, I would still go with the lower power.