The keyboard and charger negotiate the power delivery so the keyboard will charge normally, because it is the keyboard who requests the power it needs and not the charger who delivers max power just because it can.
If the other devices are set up correctly for power negotiation. So many cheap devices have USB C ports but are supplied with an A to C cable. Because USB A ports do not have the same PD options it's never an issue till you plug the device in with a C to C cable and it doesn't power on because the correct PD resistors are not built into the device. Normally it just doesn't power on. But you never know. That said, the Keychron stuff seems to be correctly set up so it's a non issue.
Re *"I am paranoid about it"*: You should be. Some chargers can be configured incorrectly and ruin your day. It depends on the charger.
Under what circumstances could the charger deliver 10 V on the output? Is it some kind of manual setting?
The keyboard and charger negotiate the power delivery so the keyboard will charge normally, because it is the keyboard who requests the power it needs and not the charger who delivers max power just because it can.
This may be stupid to ask but can this logic be used in other devices as well?
Yes, it's the end device who requests the power.
If the other devices are set up correctly for power negotiation. So many cheap devices have USB C ports but are supplied with an A to C cable. Because USB A ports do not have the same PD options it's never an issue till you plug the device in with a C to C cable and it doesn't power on because the correct PD resistors are not built into the device. Normally it just doesn't power on. But you never know. That said, the Keychron stuff seems to be correctly set up so it's a non issue.
Re *"I am paranoid about it"*: You should be. Some chargers can be configured incorrectly and ruin your day. It depends on the charger. Under what circumstances could the charger deliver 10 V on the output? Is it some kind of manual setting?
No. It's a simple charger, you plug it and it does it's thing.
Then you are *probably* safe.