For planars you need space from the front wall. You also need space for the seat from the planar, ideally.
Some planars the back wave can cancel front and create a bass null in some rooms.
Ideally I like planars to be at the right width to disappear and play as one coherent wide plane with sound starting behind coming in front as of the speaker is not there.
I found Maggies (or at least mine) were real happy in a shoe box shaped room, maybe a third of the way out. Didn't need to be spread wide. Excellent dimensionality and height - I remember being somewhat stunned when I first heard them set up properly - Ella Fitzgerald standing there between the two panels.