The present disclosure relates in some aspects to methods, cells, and compositions for preparing cells and compositions for genetic engineering and cell therapy. Provided in some embodiments are streamlined cell preparation methods, e.g., for isolation, processing, incubation, and genetic engineering of cells and populations of cells. Also provided are cells and compositions produced by the methods and methods of their use. The cells can include immune cells, such as T cells, and generally include a plurality of isolated T cell populations or types. In some aspects, the methods are capable of preparing of a plurality of different cell populations for adoptive therapy using fewer steps and/or resources and/or reduced handling compared with other methods.