Multiple users can use the same account although we strongly don't recommend doing so as our insurance policy does not cover accounts with multiple users. Why? Having more than one user to an account can be very risky for a number of reasons - 1. you will have to give out your 2FA code 2. your password will also be with others 3. you have no control over your account/coins etc. 

Yes you can use your MCW account on multiple devices although your 2FA needs to be set up on your own personal device - insurance does not cover 2FA on multiple devices.