Mixing signals on an AB 1762-IF4

I'm using a 1762-IF4 4Ch analog input module with an Allen-Bradley MicroLogix 1400 PLC .

Questions:
1. Should I use isolators on each channel if all of my 4-20mA inputs are 4-wire transmitter w/differential inputs? E&H Pro_Mag flow meters are the transmitters.

2. When/where do the COM terminals connect to? The wiring arm has two terminals marked COM but the manual doesn't show them connected to anything on 2-wire, 3-wire, or 4-wire transmitters.

3. Should isolators be used if I mix 2-wire and 4-wire transmitters on the same module?

Thanks