Two screens side by side and my neck only hurts on one side, where are you supposed to put them?

Two things that matter as much as position and get set once and never revisited.

Distance. Further away than most people sit. A common guide is roughly an arm's length from the screen, and further for a larger one. Sitting too close is a large contributor to eye strain and to the head-forward posture that produces neck ache, and with two screens it also makes the turn to the second one much bigger, because the angle grows as you get closer.

Moving both screens back ten centimetres often does more than repositioning them.

Height. Top of the screen at or slightly below eye level, so your gaze runs slightly downward. Both screens at the same height if they are side by side: a mismatch of a few centimetres means a small head tilt every time you look across, all day.

And if you wear varifocals, all of the above changes: the reading portion is at the bottom, so a screen at standard height makes you tilt your head back to see it. Lower is usually right, and it is worth mentioning at your next eye test since there are lenses made for this.

On your existing ache: give a changed setup a couple of weeks. It will feel wrong at first because you have adapted to the old one, and that is not a sign it is incorrect.

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.

Stacking is the option people forget and it is genuinely good for a specific case: a secondary screen you monitor rather than work in - chat, logs, a dashboard, documentation you glance at.

What it buys:

No horizontal turning at all. Your primary stays dead ahead. Glancing up is a much smaller movement than rotating, and eyes do more of it than the neck does.

Desk depth. Two side by side pushes you back or forces a shallow angle; stacked uses vertical space you already have.

What to watch:

The top screen must not be high. Looking up for extended periods is worse than looking slightly down. The top of the upper screen should still be around or below eye level when you sit up, which usually means the primary sits lower than people expect.

It is bad for a second screen you actually work in. Long stretches looking up will hurt.

It needs an arm or a stacking stand, since most monitor stands cannot do it.

So, for your split: main work left, chat and reference right - either primary centred with the secondary angled beside it, or primary centred with the secondary above. Both fix the rotation; pick on desk space and on how often you look across.