Do larger planar speakers produce more accurate sound?

If by “clarity” you mean an absence of resonance that makes for a murky or muddled sound, panels and compression midrange drivers can be very good.  The very best compression drivers, such as those made by Western Electric, International Projector Company, YL, G.I.P., Goto, manage to substantially avoid nasal resonance that color some compression drivers and deliver clear, detailed and well textured sound with a sense of ease.  These drivers must be matched to very nimble and clear sounding woofers.  The woofers that seem to work best have light cones, and pleated paper surrounds.  The downside to such woofers is a limited excursion that mean they don’t deliver extremely deep bass.  This kind of bass is similar to that of large panel speakers which also don’t go extremely deep.   

Larger speakers play louder, but the Magnepan LRS is really a remarkable speaker and its accuracy is quite high, in my opinion. I am a musician (guitar, mandolin, uke) and regularly play five time per month with a group. My experience is with 3 models of Maggies, and a friend has some Martin Logans. I have built may and use open baffle speakers in my big system. Large doesn't necessarily mean more accurate.

I do not know if they do or not, but I really like my Maggies MGIIIa.  I enjoy the sound much more than box speakers.  I really do not care about deep strong bass; the Maggies produce nice clean bass and enough for me.

No one has mentioned line array (open baffle or not) speakers. I have only read about them, but I wonder if they might address the OP's call for "clarity" or "accuracy" or whatever magic word equates to what he wants.

I disagree with the comment about room interactions.  Most planar speakers are dipole and actually are designed for room interactions.  You send an identical  sound wave into a wall or corner and it is irrelevant if that sound wave was generated from a planar or cone speaker.  I agree completely with the comments about uniformity and ease of presentation, imaging.  I also agree with enveloping sound stage without being ever being harsh and yes they need power and dBels for all that to happen.  I've had visitors happily enveloped at SPL of 90 - 95 dB and never look at me like - what the hell.  I didn't hear QUICK mentioned and especially in the mid bass there is nothing like them.  The couch, chair and floor will vibrate -  musically and instantly.  Just don't expect anything to shake and rumble even with larger planars.  But shake and rumble generally ain't music anyway!!