Precision measurements of the intensity and polarization of the cosmic microwave background (CMB) contain a wealth of information about the early universe and its development over time. Over the last twenty years, telescopes with apertures around six meters in diameter observing from the ground at microwave frequencies, including the Atacama Cosmology Telescope (ACT) in the Atacama Desert in Chile, have begun to contribute heavily to CMB studies on medium and small scales. Their success has driven the development of next-generation millimeter and submillimeter observatories like the Simons Observatory (SO) and the CCAT Observatory. This dissertation outlines the development of new optical designs for the cryogenic receivers and data acquisition hardware, software, and procedures that will enable the Prime-Cam instrument on the CCAT Observatory’s Fred Young Submillimeter Telescope to become the premier mid-scale observatory at submillimeter wavelengths. On the optical design side, exploration of the use of biconic lenses to correct the residual astigmatism of the telescope optics led to the adoption of a biconic lens for an upgrade to SO but concluded that they were not necessary for the 350 GHz module for CCAT. A new design for the Epoch of Reionization Spectrometer, which will use a Fabry-Perot Interferometer (FPI) for line intensity mapping of ionized carbon near the end of the epoch of reionization, was also developed to account for the unique needs of the FPI. On the data acquisition side, the designs for hardware and software needed to operate Prime-Cam remotely and efficiently are presented along with the current status of their implementation. In addition to adapting much of SO’s software to work with Prime-Cam, new software was developed for capturing and storing data from Prime-Cam’s RFSoC warm readout system with the largest number of polarization-sensitive microwave kinetic inductance detectors ever deployed for astronomy. This work concludes with a summary of the first stage of a search for time-dependent, isotropic birefringence in short-duration ACT polarization maps of the kind that could be caused by axion-like dark matter particles (ALPs). Using a power spectrum based estimator, a polarization angle has been calculated for nearly 13,000 ACT depth-1 maps covering five years of observations, and work continues to convert that angle timestream into constraints on ALP properties. Measurements of polarized millimeter-wave emission by ACT and future observatories holds great promise for discoveries in cosmology and astrophysics in the coming decade, including further studies of parity violating effects in galaxies and in the CMB which could be caused by dark matter or new physics.