no la bro... just the truth, you know me
There are some shops you can trust, but majority of them nowadays are just to make a quick buck out of you, sadly.

Correct, those are what you should spend money on, gears, protectors especially for you and then your bike, in that order. The next best thing you can spend money on will be your tyres (good tyres helps a lot during rain, coners and especially braking).

Melaka to KL is not that far bro, with the standard Z250 you can reach in about 1 hour. it's good enough because any faster, you'll get a summon... which is so not worth it.

yes, it does but too little to feel... the most you can feel will be at gear changes... smoother, easier and less noise.

NGK has 3 types of plugs, the normal, the type R and the red color box for race purpose. try check if they have the red box type for Z250.
On my own personal test from majority of brands, I find that Silkolene & AGIP are the best.

Honestly speaking, Motul, Shell and a lot of good name brands has knock off... do buy from a trusted workshop. I assume you might kena the knock off or your engine got leak or burning engine oil.

Now, some people might disagree when I say this, the best SAE rating to use in Malaysia will be 15w-50. This SAE rating would be just right for our weather. 10w-40 is too thin and easily burnt off... while 20w-50, you might need to start you engine a couple of time during cold. If you are using a V-Twin engine, there are new oils which have XXw-60 rating, this will be the best choice but if you are using Harley then get the 20w-50 specifically designed for Harley V-Twin.

Please note I have a lot of bikes and no car. hehehehehe
but to me best to use original because afraid that the ciplak one might decrease engine performance, unless you tested the ciplak one before and got umph.