Despite several decades of active experimental and theoretical studies of rare-earth orthoferrites, the mechanism of the formation of specific magnetic, magnetoelastic, optical, and magneto-optical properties remains a subject of discussion. This paper provides an overview of simple theoretical model approaches to quantitatively describing the structure-property relationships, in particular, interplay between FeO$_6$ octahedral deformations/rotations and main magnetic and optic characteristics such as Néel temperature, overt and hidden canting of magnetic sublattices, magnetic and magnetoelastic anisotropy, optic and photoelastic anisotropy.