I’ve got several different 20,000mAh battery packs that each have 2 USB-A outputs and one USB-C. With any of the battery packs I’ve had no trouble using the two USB-A outputs to power ~350 LEDs for around 10 hours. Not at full brightness of course but still plenty bright, with a maximum current draw of around 2.4A per USB socket (but generally lower, maybe around 0.8A or so depending on the pattern). There’s not much point me recommending them though unfortunately as they’re quite old and no longer available to buy anywhere.
I’d suggest just looking around for a powerbank with dual USB-A outputs that has the highest combined 5V current output you can find. I say “combined”, because many/most powerbanks have a combined current limit when using multiple outputs that is a lot lower than the sum of the individual outputs. For example, a powerbank might say 3A quick charge on one USB-A and 2.4A on the other, but if you use both at once the total current it will deliver might still only be 3A. You’ll have to read the powerbank specs or test it to find out for sure. It’s difficult to find a powerbank that can handle dual 3A USB-A output, and if you do find one it’ll likely be pretty expensive.
Note that if you’re cutting a USB cable to connect the powerbank to your LEDs, make sure you short together the two data wires (normally the white and green ones), as I believe that signals to the powerbank that it should supply up to 3A, instead of the normal 2.4A limit. That is assuming your powerbank can deliver 3A of course!
To make use of a USB-C PD output your best option is probably a “PD decoy/trigger” that handles the PD negotiation for you. For example, something like this, or if you want really small, this one. I have a few decoys that I’ve used successfully with USB-C for 9V and 12V projects but the ones I have don’t support 5V so been able to try them with LEDs. The one I’ve linked does allow 5V and I’ve been meaning to get a couple to try for this reason. You should in theory be able to get 4.5A or more from a USB-C PD @ 5V.
I haven’t measured the PixelBlaze power draw so can’t help you with that question sorry. It should be a lot less than the power required by the LEDs though.