U2720Q, USB Type-C PD protocol and its compatibility?

@Michjoe  You might want to find some technical articles if you're really curious about USB PD, but at a high level, the USB PD protocol works with the power source starting off at the USB standard of 5V.  This way even if you connect a regular USB device that does not support USB PD to a power source that does (such as an old smartphone to a USB PD charger), then the source will only provide the standard 5V that USB has always used.  But after that initial connection, the power source will advertise the USB PD voltage levels it supports and the maximum amperage it can provide for each voltage.  The device being charged then has the option to request any of those other choices.  This design prevents the power source from sending a voltage level that the device being charged can't handle, and also prevents the device being charged from trying to draw more amperage than the source is designed to provide (voltage is controlled by the power source, amperage draw is controlled by the device being charged, at least up to any throttling limits the power source might have).

USB PD is currently at USB PD 3.0, but yes the versions are compatible with each other.  In some cases if you have a power source that only supports an older USB PD version and a device that can use features of newer versions if available, that device might not charge as quickly if it can't use those new features.  The Programmable Power Supply (PPS) capability is one example of this.  And there have been other improvements too.  For example, there are USB-C multi-purpose hubs that can either draw power from the laptop or provide power to the laptop through a USB PD power passthrough port.  Earlier in the USB PD standard, if the power source of that device changed between the laptop and an external power source, then the hub basically had to reboot.  So if you had USB devices like external hard drives connected through the hub, that would cause them to briefly drop offline, which could be a problem.  Newer USB PD standards don't require this behavior anymore.

Yes, you can charge a T490s from a U2720Q.