Pretty easy from my experience since (as mentioned already) there are no annual vehicle inspections & AFAIK mod laws are not as strict as compared to some eastern states.
Cops aren't too bad at all from my experience & reading around, for one I have never seen/heard about cops in WA doing specific 'defect operations' here, the do the usual RBT/booze buses operations & camping with speed guns, but never those operations that target nothing but people with modified cars (& usually only imports or V8s, while your rusty bucket Camry can go through unnoticed) as seen from TT/ACA by eastern state police (Vic in particular).
WA has the lowest fines for minor speeding I believe, under 9km/h over is only $75 with ZERO demerit points (compared to most eastern state which will be ~double the fine & have atleast 1 demerit points), so you never have to worry about losing your license for accidently creeping over the limit, although this might change in the future with the 'please think of the children' group crying about people doing 5k over & killing babies *roll eyes*.
Also this is the only state in Australia where radar detectors are legal