Hi,
For #2, by default any table other than system table will be stored as column store.
For #3, SAP HANA Live comes with two default business and developer roles. Also we have authorization assistant to further customize them.
For #1, afraid there is no formula defined to estimate the size of SAP HANA for purely HANA live implementation. SAP HANA live meant for enhancing the reporting capabilities using existing data which already stored in SAP HANA database or planned to bring in.
For a new implementation, you may go with the regular SAP HANA sizing exercise. But I will touch back on the sizing part again.
Hope it helps.