MOSFET topology to switch between voltage and ground?
Most people drive the rungs of an R2R ladder with standard CMOS output pins.
The "topology" directly connected to that output pin is generally a static CMOS inverter:



where 'Q', Vdd, and Vss are physical pins you have access to, and 'A' is internal node of the chip.

Some of them use a few CMOS output pins on a microcontroller to directly drive the R2R rungs.
The rest generally use a few output pins on a microcontroller to send data to some sort of latch chip or buffer chip, and then the CMOS output pins of that chip drive the R2R rungs.
Often the latch chip is the 74HC595 (if their "arbitrary positive voltage" is in the range of 2.0 V to 6.0 V) or the HEF4069 / CD4069 or the HEF4094 / CD4094 (which can handle "arbitrary positive voltage" in the range of 3.0 V to 15 V).