back to the OP's question.
R2R DACs run each of the 16-24 bits through a specific resistor pair combination to create the analog counterpart, then sum and filter the result.
Bitstream DACs use pulse density modulation on a single resistor. The more "1"s the higher the voltage. It too is summed a filtered. This is also how light dimmers work and how your car's fuel injection works.
depending on how technical you are you can get the original paper from Philips online. R2R goes back to Bell Labs for t-carrier.
There are benefits to either. in general i would argue that the DAC chip itself is th least important component of the system. Just as i have made tubes, FETs and BJTs sound basically the same, those two can sound very very similar until you get to ratified air of quality. Its all abotu power supplies, filters, I/V converters (amps), timing contorl, isolation, blah, blah.
G