any idea when chargers and additional straps will be available for MARQ2? Also do you know if MARQ supports some quick charging technology like PD or PPS - what kind of charger would give the fastest charging?
Garmin's own instructions do not specify the power source.
Also these state that wall charger is ok.
Power isn't 'pushed' to the watch by the charger, the watch 'pulls' just what it needs. The rating of the charger* is just the maximum power it can output in response to that demand, not what it will actually be outputting all the time.
It's the same reason you can plug all the electrical appliances at home into the same sockets, you don't need to have different rated sockets for different appliances based on their power requirements. If your laptop needs 50W, it will draw 50W. If your kettle needs 3kW, it will draw 3kW. The fact that the socket it capable of providing 3kW isn't going to damage your laptop.
*Technically, it's just an adapter - the actual charging takes place inside the watch.
Power isn't 'pushed' to the watch by the charger, the watch 'pulls' just what it needs.
This is generally true. However, the charging current is limited by the electronics in the watch. If you give the electronics 45 watts, a lot of heat is generated unnecessarily. And this heat is the issue. This is not good for a Li-Ion battery during charging.
Regardless of this, it is better not to discharge the battery completely and not to charge it completely. If you keep it between 20-80%, you will enjoy the device much longer. Especially since Garmin obviously does not even offer a battery change for the MARQ models, although they had once announced that.