1) In general DTS package contains one or more steps that are executed sequentially or in parallel when the package is run. When executed, the package connects to the correct data sources, copies data and database objects, transforms data, and notifies other users or processes of events. Packages can be edited, password protected, scheduled for execution, and retrieved by version. So normal user privileges are enough to accomplish the task and it depends purely on level of privilege for that user on the database.
Then coming to DTS security, if you set an owner password, the package user needs the password to edit or run the package. If you set a user password, you also must set an owner password.
2) You can setup Maintenance Jobs to perform backup, DBCC checks and optimization tasks, from Enterprise Manager goto Management and there you can find DB Maint.plan to setup.
By all means refer to BOOKS ONLINE for more information.
1. Why not try it and see. Any user can create a package - remember dts is a client utility which can connect to sql server.
It's usually easier to run as sa though.
2. You can schedule a scheduled job with t-sql tasks and put any statement(s) in it you wish. Usually better to put individual operations as separate steps or call an SP to do them.
I'm not a fan of maintenance plans - would rather code the steps myself.