There is a reason for USB-C extensions not to be part of the standard. They can be bothersome in the best case and dangerous in the worst.
If you buy a Steam Deck, or the Lenovo laptop I have for work, the only charging options you have are USB C. Their standard chargers put out at least 60 45 W, and they aren’t particularly special. In fact, I’m pretty sure 20 W at 5 V won’t be enough to supply these while in use, so you will either be using battery with long charge times in between, using them with battery-assisted power for longer use times until you hit those long charge times, or using the 60 45 W or more at whatever voltage the chargers provide.
IIRC the one that came with my OLED model is 65W
It appears I did not remember correctly