For the 16 CH 12V Relay module, does the output currency mean that we could run 5VDC, 12VDC or 24VDC through the relay? What ever current we input will be the output current, correct?
1) Yes, the relays installed on the module are rated at 30VDC, 10A; so you can use it to drive anything below that range (that means 5VDC, 12VDC, 24VDC are ok. Make sure the current are below 10A though).
2) Yes, relay works like a physical switch; once connected, the current flows. The rated contact resistance of the relay is 100mOhm.