Biomolecular condensates have been shown to play a fundamental role in localizing biochemistry in a cell. RNA is a common constituent with proteins and can determine biophysical properties. Functions of biomolecular condensates are varied including activating, inhibiting, and localizing reactions. Recently it has been proposed that condensates can buffer noise to diminish cell to cell variability. Here we introduce a phenomenological model in which phase separation of mRNAs into RNP droplets can regulate the abundance of the protein these mRNA encode and markedly decreases expression noise. We place particular emphasis on how this mechanism can facilitate efficient transcription by reducing noise even in the limit of infrequent bursts of transcription, by exploiting the physics of concentration dependent, deterministic phase separation threshold. We investigate two biologically relevant scenarios in which phase separation acts to either “buffer” noise by storing mRNA in inert droplets, or “filter” phase separated mRNAs by accelerating their decay, and quantify expression noise as a function of kinetic parameters. In either case the most efficient expression occurs when bursts produce mRNAs close to the phase separation threshold, which we find to be consistent with observations of a RNP-droplet forming cyclin in multinucleate Ashbya gossypii cells. We finally consider the contribution of noise in the phase separation threshold, and exhibit that protein copy number noise can be efficiently suppressed under modest assumptions on the magnitude and time scale of phase separation threshold fluctuations.