Scalability With Mount Points

I understand mount points help scalability in easier maintenance.
By scalability do we mean more than 26 drive letters or it means adding more space to the same mount point letter on with more ease .

Can I add more space to a mountpoint if required later on by adding hard disks .

Also if one can give some pointers to good file group configuration guidelines / storage align partitions , it will be very much helpful

Further I my server CPU has 4 cores , will having 4 filegroups help me in improving system performance.


If SAN has 2 controllers , is it preferred to run data file partition on one controller and log file partition on another.

Thanks in advance.