The folk vocal aesthetic is "you and the singer in a small room." That changes the mixing approach. Less compression than pop (3-4dB instead of 5-8), more proximity (closer mic perspective, more low-mid warmth in the 200-400Hz range), and shorter, more natural reverb. The reverb should feel like a small wooden room, 0.8-1.2s decay, lower diffusion, predominantly early reflections. A long lush plate or hall puts distance between the listener and the singer; folk wants the opposite.
The acoustic guitar in folk material is a second voice in the song, not a backing instrument. It needs detail: the body resonance (80-200Hz), the mid woody knock (200-500Hz), the strum percussion (4-8kHz), and the air (10-15kHz). Over-EQing or over-compressing the guitar destroys the natural detail and makes the recording sound less intimate. The work is mostly capturing it well at the source and then leaving it alone in the mix.
Arrangement decisions are part of folk mixing in a way they aren't in denser genres. When a second instrument enters (a fiddle, a piano, a doubled vocal), it has to earn its place by adding something the spare arrangement actually needed. The mixer often functions as an editor: pulling out additions that crowd the song, automating in ornamental layers only at the moments they support the narrative arc.