Can I link second users to different accounts?

CREATE A SECOND USER

Individual account holders may add additional users to their account, either as a 2nd login for themselves (e.g., for accessing via an API) or for purposes of allowing another (non-employee/power of attorney) individual access to certain permissions within the account…

No, it is not possible to put a limit on the amount one can withdraw from their account. The only limit on the amount one can withdraw is based on the level of security on one's account…

CREATE A SECOND USER 

Yes, you can create a second user name with different market data subscriptions. Please see the IBKR Knowledge Base for more information on creating an additional user in the account holder's name…

IBKR's linked account feature provides clients with the ability to access multiple accounts with a single user name and password. While some 3rd party applications operating via the API are compatible with this structure, those that are not have the option of creating an additional user name with access to only one account. This option allows the API application to connect to a TWS session via that user name and operate as if it were not linked…