In your bottom picture, there are 4 resistor packs. Some SCA 80 to 50 boards have resistor packs, but fewer, and not enough for the number of SCSI lines in a u160/u320 drive, apparently.
Pretty sure the top one has active termination as it has a voltage regulator. I know you only need two, 10-pin, 110 ohm resistor packs to terminate narrow, 8-bit, SCSI, so I'm guessing the third 110 ohm resistor pack handles the upper 8 bits of wide, 16-bit, SCSI.
The bottom one has three, 8-pin, 330 ohm resistor packs in sockets and one 10-pin resistor pack that I can't read the resistance markings on. Pretty sure the 330 ohm resistor packs point to passive termination (also don't see a voltage regulator) and three of them can terminate a narrow, 8-bit, SCSI bus. I think the fixed 4th resistor pack is for the upper 8 bits of wide, 16-bit, SCSI. You'd remove the three 8-pin, 330 ohm resistor packs if you wanted to use the SCA drive+adapter in the middle of a narrow SCSI bus.
If you find a SCA 80 to 50 adapter with only one resistor pack (which would be terminating the upper 8 bits of the wide, 16-bit, SCSI bus) its likely intended to be used in the middle of a narrow SCSI bus or in an external enclosure where an external terminator can be used to terminate the narrow, 8-bit, SCSI if its at the end of the chain.
The issue is "upper byte" termination. The SCA 80-pin and some 68-pin wide drives need the extra 8 data lines terminated when connected to a "narrow" 8-bit bus.
If the SCA drive is at the end of the narrow SCSI chain I'm fairly certain it needs both the upper and lower bytes terminated, upper terminates the unused wide SCSI data lines and lower terminates the data lines in use on the narrow SCSI bus.
But if the SCA drive is in the middle of the narrow SCSI chain you would want the adapter to only terminate the unused upper byte wide SCSI data lines.