I'm not sure what USB has to do with anything. Were you looking to be able to remotely control the power supply over USB? An ATX power supply outputs 5V and can be connected to a Pi very easily, either through the 5V input on the GPIO header or through a Rube-Goldbergian collection of adapters that go from the power supply to the power connector on a Pi.

If you want stable power with more than enough amps to power multiple Pis then a beefy DC power supply is required. Anything affordable is going to come in the form of a switch-mode power supply, similar to this. USB "chargers" can't provide enough amperage to multiple ports simultaneously.

This is the power supply I purchased https://www.amazon.com/gp/product/B07KC3KSHP/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&th=1