Direct digital-to-physical synthesis of precise RF waveforms with challenging spectral purity, timing and amplitude control requirements is demonstrated for mm-wave transmitters and cryogenic qubit controllers. The article focuses on four core architectures common in both application domains: Cartesian in-phase/quadrature (I/Q), polar, RF digital-to-analog converter (DAC), and harmonic/subharmonic modulation. A thorough systems analysis is conducted for both applications for fundamental architectures. Tradeoffs in energy efficiency, signal integrity, waveform synthesis, and error mitigations are analyzed. The parallels between innovations in one application domain and advances in the other are highlighted throughout the article to illustrate the potential for coevolution of mm-wave arrays and qubit controller hardware.