It depends on how you use them, and your one-sided ache is the diagnosis.
If you use one screen most of the time: your situation, put that one directly in front of you, centred on your body, and the secondary one angled in beside it. Not symmetrical, and that is the point: you are aligning the arrangement with where your attention actually goes rather than with the furniture.
The join-in-the-middle layout is right only if you genuinely split your attention evenly, and almost nobody does. Everyone has a main screen; putting the bezel where your face should be means spending the day rotated.
If you genuinely use both equally, the symmetrical arrangement is correct and the fix is different: angle them inward so both are roughly perpendicular to your line of sight, and sit slightly further back so the outer edges are less of a turn.
If the second screen is reference material you look at occasionally, it can go further out, or it can go above.
The principle underneath: your head should be neutral for the thing you look at most, and turning should be the exception. Swap them today, cost nothing, and see how your neck is by Friday.