Chemical systems with mixed quadratic and cubic autocatalytic feedback support simple reaction-diffusion fronts under suitable circumstances. If reactant and autocatalyst species have equal diffusivities, then from typical initial seedings, the system selects between two different types of fronts depending on the relative strengths of the two channels. In terms of the parameter mu = k(q)/(k(q) + k(c)[A](0)) where k(q,c) are the rate coefficient for the quadratic and cubic channels and [A](0) is the initial reactant concentration, then with mu>1/3, the system selects a "quadratic type" front determined only by the quadratic channel, but for mu<1/3, the system adopts a "cubic type" front in which both channel contribute. For pure cubic autocatalysis (mu=0) these fronts become geometrically unstable if the diffusivity of the reactant exceeds that of the autocatalyst. The present paper examines the selection of wave type and wave velocity and the onset of lateral instabilities of smooth waves for mixed autocatalytic systems for arbitrary reactant and autocatalyst diffusivities.