MARQ2 charger type?

Marq 2 indeed has fast charging. 1h to full.

I'm just using my Samsung Galaxy S21 Ultra super fast charger with the Garmin cable.

For straps any 22 mm and previous straps from Marq Gen 1 work.  For chargers I ordered two but the Garmin website still says 3 to 5 weeks, needless to say my order hasn't ship yet.  Also like mentioned before the Marq Gen 2 charges under an hour.

Oula said:

I'm just using my Samsung Galaxy S21 Ultra super fast charger

How many amps does the device supply ? Even if the charging electronics in the clock regulates the charging current, I would be careful with this completely oversized charger. Keep in mind that your phone has a battery with a multiple of the capacity than the battery of the watch. I think that the battery of the watch should have about 500mAh. It should not be more than 2C (1Amp).

Samsung Super Fast charger will only give the high current to compatible Samsung devices. 

Also these state that wall charger is ok. 

https://support.garmin.com/en-US/?faq=JNhaDUyHtQ5Nn2CoRXYFv8

https://support.garmin.com/en-US/?faq=DPw2iMyYpS6drjfdzWlr4A

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.

NeilJonesOnline said:

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.