Is a singular LUKS volume with different passwords that unlock different filesystems possible?
No, LUKS does not support this. What you are looking for is plausible deniability, similar to what VeraCrypt supports. LUKS does not support this, with the reasoning explained in section 5.18 of the official cryptsetup FAQ. Their reasons for not supporting this boil down to the fact that it is difficult to use plausible deniability with hidden volumes correctly. For example, if you don't write to your dummy volume in a while and the timestamps show this, the deniability is broken.