Can a Power bank like this be used for a 12v amp.board?

People, I'm looking at power sources for a relatively small Bluetooth speaker build and noticed these

18W Power Bank, ROMOSS 20000mAh Portable Charger, with 3-Port Charge and Recharge, External Battery Pack Fast Charge for Nintendo Switch iPhone iPad Samsung Galaxy Google Pixel and More, White: Amazon.com.au: Electronics

Not knowing an awful lot about these, I cannot see why one couldn't power an 12v 2*30w 1*50w 2.1ch class d amp and a Bluetooth board? Just unsure if there circuit in the power bank would prevent this at all, or when plugged in if it would prevent use of the speaker. The speakers I was looking at were 2* 2in full range drivers and a 3.5inch mid bass in a .1cuft box so I don't think it will I will be pushing the limits of.rbe board or drivers.

Price also seems to be cheaper that buying the under/over charge circuit and 3-4 18650 batteries

Any advice from the experts out there that may have tried or looked into this before?
 
I think this is the sort of thing. It tells the USB PD circuit to use the selected voltage instead of just the standard 5v

NZ$ 7.45 | Type-C USB-C PD2.0 PD3.0 to DC Spoof Scam Fast Charge Trigger Polling Detector USB-PD Notebook Power Supply Change Board Module
AliExpress

I think you'll be better off hacking in a step up converter to the battery directly