Hi,
1: It's not required to configure the track-ip for failover of redundant interface. They failover depending upon the link failure.
2: NSRP VSD level track-ip and all are mainly used when you use NSRP cluster of 2 devices.
3: If needed then you can configure the trac-ip at interface level which will bring whole redundant interface down. Or if it's configured a particular interface then that will be brought down.
Thanks,
Vikas