Just out of curiosity, is this the battery you were referencing? This is my current plan and wanted to see if you had any thoughts on it.

I use this for my pi4 8gb builds:https://www.amazon.com/Raspberry-Battery-Standard-10000mAh-Expansion/dp/B07Y213F8S/ref=sr_1_2?crid=3AQQ5FQ9GZ0LI&keywords=makerfocus+battery+bcm&qid=1649448108&sprefix=maker+focus+battery+bcm%2Caps%2C95&sr=8-2

I've also plugged those low-amp phone charger backup bank thingers in to the charge port of the BCM, and as long as you have enough charge in the on-line battery to keep you going while charging, you can work off it like a pass-through. Your charging will never really catch up, but it will let you power the device from the low amp battery pack, if indirectly.

I power quite a lot from that setup. The Pi 4, a wired mechanical keyboard (with backlit keys), wired mouse, 7" touchscreen, and an unpowered usb 3.0 hub with a couple usb thumb drives for storage.

I also have a 15w solar panel that will charge the whole mess up directly from the sun.