I need to vet existing USB-C hubs for the following application:

USB-C Smartphone <- [ USB Hub ] ...

[ USB Hub ] USB-A -> USB-C Storage medium (2x)

I need the (android) phone to be able to mount these two USB-C devices (which, unfortunately, require USB-A -> USB-C connections) at the same time. The current solution is _slow_ to mount and sometimes fails completely.

I can't control the USB hardware of the phone and the connected devices, but I can control the hub selection. I'm looking for tips re: USB hardware/software testing procedures.

In the short term, I need to choose a commercial hub, but in the long term, will design and build a custom hub. Recommended resources + techniques in the vast world of USB would be greatly appreciated!