There are some common pitfalls in so-called "Fast Charging" adapters:

• Many adapters does not support dedicated Fast Charging protocols for Huawei (FCP, SCP), MediaTek (Pump Express), OnePlus (Dash Charge, Warp Charge), and OPPO (VOOC, SuperVOOC). In my case, most of them only either support Qualcomm's QuickCharge 3.0 or USB Power Delivery (PD).
• Many multiple-port adapters "cheat" by lowering the overall wattage power when charging multiple devices. This is intentional for safety reasons, but many of them cheat by not working at Fast Charging speeds. One common example is a double-port adapter that only runs Fast Charging at 18W when one of them is being used, or else, they default back to 5V-3A (15W) which is not considered as fast charging by most devices.
• Samsung's official 25W "Super Fast Charging" adapter do not work well with non-Samsung devices. I cannot make it to work properly with iPhones and vivo phones compared to another smaller, 20W PD adapter which I got for free.
• There's a room for improvement to replace single-port chargers into multiple ones. It doesn't have to be a GaN, though.

I recently received many still-functioning fast chargers. I don't want to turn them into e-waste, so I decided to put down some large, informational labels to maximize my fast charging strategy.

The good news is that most of our devices are compatible with Qualcomm's QuickCharge (QC) 3.0 and USB-PD. So these chargers are still mostly good for us.

I even created a dedicated infographic about these adapters to let my entire family know how to fast charge their devices.