I forgot to mention that. I already own the Fuji recomended Anker PowerCore 20000 PD and use it to charge while the camera is in the bag. But still a little clunkly setup if I want to walk around with the camera out.
It's also great to just charge the camera over USB-C.
Having a C to C connector would charge faster if the battery supports The Power Delivery (PD) spec for USB-C. I don't expect that battery is damaging your device, but if you want faster charge speeds I would recommend Anker's Powercore+ PD line of devices.
I have the I have the 20000 PD and it charges decently fast for a battery, topping out at about 26 watts (less than half the speed of the MBXP included 65W charger, many phones top out at 15-18W).
All that said, the battery you're using is probably fine if it's working for you.
I use this one for both the Pixelbook and Pixel phone. No problems, charges fast, not too huge. Too bad you massed a half-price sale on it last week!