The whole idea of these drives for a NAS is if you're using it in the recommended products, those products will configure the drive if it needs either of these features.
TLER will cause the drive to report a CRC error more quickly when encountering a sector read error, rather than continuing to make attempts. In RAID 0, or single disk use, this is not a great idea. It's better for the drive to error correct because there is nothing above the disk level that can correct for it. Whereas with RAID 1, 4, 5, 6 or RAIDZ there is at least the possibility of correcting for a failed sector. The implementation is what will determine whether it actually does or not.
It's kinda hard to test these sorts of things, because there isn't a way to get the drive to, on command, issue a CRC error and see what the handling is by layers above (RAID and file system). i.e. would software RAID (including mdraid) either 1, 4, 5, or 6, automatically use the mirrored copy of a CRC'd sector, or rebuild it from parity? And if it rebuilds from parity, does it then attempt to write out that chunk forcing the drive to write those sectors, which would cause any persistently bad sectors to be automatically removed from use by drive firmware?
I don't know. But in theory that's how it would work. It would be nice to know what happens (and no doubt it depends on the RAID implementation).