Narrow and Ultra are not mutually exclusive terms. Narrow and Wide are; they refer to how many bits are passed in parallel on the SCSI bus (8 vs. 16), which has an impact on bandwidth (wide doubles narrow bandwidth) and number of SCSI IDs (again, 8 vs. 16). Ultra refers solely to the bus speed. Single-ended and LVD (Low Voltage Differential) are something else again, but are definitely not intermixable, though LVD drives are (almost?) always backwards compatible with SE chains. It's possible to intermix wide and narrow devices on the same chain without degrading the wide devices, but you have to make sure that you don't accidentally chop off the wide portion of the bus before it gets to the wide devices while still terminating both the narrow and wide parts of the bus.

All that being said, you're definitely right that the LVD drive is not performing optimally, unless the 19160 has multiple channels, which I'm pretty sure it doesn't. I would also be concerned about the termination that's going on inside that case, but it's possible that it's being done right, especially since the 19160 ships with an LVD cable with integrated terminator. I'd imagine that a 68-50 pin adapter is being used for the CDROM, on that cable, right? That's the right way to do it.