Rman backup incremental level 1 for recover of copy with tag

I have done some searching on the web with documentation saying when running incremental level 1 for recover of copy backup may need to turn block change tracking on to avoid performance issue. Currently we are having the block change tracking as disabled. However, we did raise oracle SR and the support personnel telling me that the blocking change tracking only has 7 block and incremental level 1 for recover of copy will need unlimited blocks and thus the block change tracking should be disabled. So I am a little bit confused if we do need to enable the block change tracking or leave it disabled? Below is our backup script. Also, when they say it will have performance problem, does it just mean it will take more time to do the restore and recover? Or, is the performance problem means it will have issue restoring at all? connect target / set echo on; configure backup optimization on; configure retention policy to recovery window of 5 days; configure controlfile autobackup on; configure device type disk parallelism $PARALLELISM BACKUP TYPE TO COPY; configure datafile backup copies for device type disk to 1; configure archivelog backup copies for device type disk to 1; configure channel device type disk format '${RMANBACKUP_MOUNTPOINT_FULL}/full/datafile_%U.bkp'; configure controlfile autobackup format for device type disk to '${RMANBACKUP_MOUNTPOINT_FULL}/full/full_controlfile_%d_%F.bkp'; run { sql 'alter system archive log current'; backup incremental level 1 for recover of copy with tag 'phoenix_oracle_backup' database; recover copy of database with tag 'phoenix_oracle_backup'; sql 'alter system archive log current'; backup as backupset format '${RMANBACKUP_MOUNTPOINT_FULL}/archivelogs/%d_%h_%e_%s_%t.arc' archivelog all not backed up; #Force is to ignore I/O errors delete noprompt obsolete device type disk; delete force NOPROMPT expired copy; delete force NOPROMPT expired backup; crosscheck backup; crosscheck copy; } configure backup optimization clear; configure c