Optimization of component values in LPF
In principle, I know what you mean. However, the answer is not easy because it depends - more or less - also on the corresponding operating frequency. Here are some basic rules:


The values of the resistors and impedances (at the operating frequencies) should be large (small) if compared with the output (input) impedance of the opamp.
Preferred component ranges are: R=(1E2...1E5)ohms and C=(0.1...1000)nF.
More than that, preferred maximum "component spreading" values are 0.1, 1, or 10.
If the input impedance of the filter circuit is an important design parameter depends on specific application requirements. If necessary, an additional buffer can be used or the (known) signal source resistance is to be considered as part of the design process.    
In your specific example, there is another criterion which matters: For frequencies far above the pole frequency (stop band of the lowpass) a part of the input signal is coupled DIRECTLY to the output of the opamp (through C1). Because for rising frequencies the opamps open-loop gain continuously decreases, we have an increase in the opamps output impedance - and there will be a remarkable unwanted signal voltage drop across this output impedance. Hence, the attenuation in the stop band becomes worse for high frequencies (stop band). For this reason, the feedback capacitor should be as low as possible. This is a well-known (but not always documented) disadvantage of the Sallen-Key lowpass topology.
As you can see, there are several (partly conflicting) optimization strategies. Therefore, there is no general answer to your question.