Efficiency as in sun hours? Pretty standard about 3 I guess.

About 20% maybe.
But generally when looking at penal, it is not mentioned much about the efficiency. At least from my point of view.
It is more about the output of the panel 500W, 550W, 600W or 650W but then again the panel size is also slightly different.

Let say a 7kw system, so we have a 3 sun hour a day.
So it will generate about 7x3 = 21kwh a day. So in a month, it will generate 21*30=630kwh, and probably offset your electricity assuming 50sen per unit, by RM315.

Hmm... its long time investment but also not too long.
As long as one can recoup in 10 years time from the NEM then it is fair enough. There is little point to get the most efficient panel from  consumer point of view. Unless you have very limited roof space, but generally in Malaysia, our house is consider large 

one can always wait... and new stuff will always appear...

when ready to commit... just get whatever in the market lah... if new design already available, can try nego since 'old stock'...

yes... but when can we buy it?

"Longi has broken the world record for solar cell efficiency 16 times since April 2021. It claimed the world’s highest efficiency for silicon cells in November 2022, with a 26.81% efficiency rating for an unspecified heterojunction solar cell."

can we buy the old 2021/22 world record panels?

imho... if ready, just commit and don't look back... roi within 5-6 yrs is really a great project...