Determining maximum table size, type of engine and type of indexes supported
SQL Server has B-Tree indexes only. Other types are hardly used day to day.
All maximum capacity specs for 2008 are here: there is a link to SQL Server 2005. Note SQL Server does not have "limits" apart of disk space for size of the DB or a table.
Express differs in other ways: see editions
Like Sybase, Oracle, Postgres, SQL Server is a single engine. As an approximation, InnoDB is MySQL's closest in concept


Note: if you come from MySQL, do not make assumptions about SQL Server. It (like other RDBMS) are more complex and mature then MySQL in many respects