How to decide on laying out copper area when working with Wifi/RF chips & how to use a guard ring?
Typically it is not horrible practice. It's not that the practice causes parasitic inductance that could be a problem (because it's always a problem). The practice reduces parasitic inductance by increasing capacitance which is generally good. It is the extra capacitance that could be a problem for sensitive circuits that operate off capacitances of several pF or less like oscillators.

Specifically for traces actually carrying RF though, such as antennas, you do need to pay attention to everything but if it is a chip or module (especially modules) you may not need to be so cautious around most of the component. Check the datasheet guidelines. Besides, 2 layer boards are not the place for RF anyways.

Guard rings go around sensitive traces that operate on very low current (typically high impedance inputs but also RF); Currents so low that leakage currents from other nearby things through the PCB dieelectric can interfere. The guard ring tied to GND shorts out these currents before they can reach the high impedance input. Apparently you are not supposed to put soldermask over guard traces since that provides a path around (or over them), as does surface contamination.

Rick Hartley Grounding:
https://www.youtube.com/watch?v=ySuUZEjARPY&amp;list=PLlD-hnyodqSf7D9zPVviYaOaDZnWxkDYx&amp;index=21&amp;t=3466s