It think that one thing that may be confusing the OP is his lumping Amps, DACs, and Speakers, as electronic devices. Amplifiers and dacs are electronic devices. Speakers are an electromechanical device, converting electrical energy into mechanical energy.
With electrical devices, we have very quantifiable measurements that are highly correlated and inform us of their qualities. With speakers, the audibility of the different measurements we make become less correlated, in large part because every room is different, placements within rooms different, resulting in vastly different sound, even for the same speaker, when moved from room to room. We know that in general, most people prefer speakers with a flat frequency response that continues off axis. That is correct in most cases, but say you have a large room that is extremely over dampened and listen from 5 meters away. A flat speaker with smooth off axis response will lack high end response, while a tilted up speaker will sound correct.
So while we can predict with strong certainty if an amplifier or dac will work well (is the SN ratio sufficient, does the amp have enough power to not clip), we cannot predict what room a speaker will be put in, the setup of the speakers, or the furnishings in the room. This is why in home speaker auditions are so important for speakers, but not for dacs, amps or other source components.
Finally, the OP asked if two speakers of the driver design and layout will sound the same. The short answer is sometimes, maybe. You can build two identical speakers, but use two different crossovers, say a 6db/octave versus a 24db/octave, which will give the same on axis response, but entirely different off axis responses, resulting in very different sounding speakers.