Generally the delay in CMOS technology is the capacitance...becasue we need time to charge and discharge...when added some extra circuit(even as small as inverter) it will increase your delay.....
MAybe u mean that inverter is used to build buffer so it's a delay element....
Well for 14bit DAC u can build it using R2R network, it's smaller but be careful with the op-amp, the non-lineraity and offset can disturb your DAC output, and resistor matching is very important