Can you charge an iPad and connect a USB-C device at the same time?
The answer here is it depends.

The device you have pictured above is designed to be connected into a computer (Mac or PC, it doesn't matter.)

Unless otherwise stated that the port supports Power Delivery (PD), it will only supply a limited amount of power.  In one recent answer I wrote, the iMac will only supply 15W of power.  However, you'll have to get the exact power specs for your particular machine.

All devices have some sort of power draw; even a flash disk has some power draw, usually in the milliamp range (200 mA or .2A).  However, if you exceed the power limitation of what the port can supply, it will end up disconnecting devices.

Assuming that you're using an iMac that can deliver up to 15W, the iPad has a requirement of 10W meaning you have 5W extra to spare.  You should be able to use (not charge) another USB device like a flash drive (5V * .2A = 1W)