Answer: The resolution of the WF 2144 varies over the range and can't be expressed in bits or ohms. Instead the resolution is expressed as a error that varies over the range.
The WF 2144 works by connecting resistors in parallel instead of series to achieve the desired resistance. This increases the range dramatically, with a very small error for low resistance values, and a larger error at higher values.
By connecting two channels in series, it is possible to achieve an even lower error over the whole range, we call this "Enhanced Mode".