It depends. Airlines do upgrade passengers to Business, especially from Premium Economy.

I was on a business trip to US once, flying Cathay via HK. Was flying Premium Economy, and then got upgraded to Business class at the boarding gate. Maybe because I'm at the first row of Premium Economy and my ticket was booked together with my friend (who is flying Business).

On the other hand, I flew MH Business to Mumbai, India once and the cabin has few empty seats

Okay, I completed the Comparison table between EM/KF/AM for some popular destinations:
Frequent Flyer Comparison

All amounts are for return flights, based on the cheapest redemption ticket (Basic on EM, Saver on KF, Standard on AM). No doubt these miles required might not be available when you book due to availability / wishlist issues, but it serves as a good benchmark.
(p.s. I don't have sufficient miles in my AM account that's why I'm unable to check the taxes required for J class redemption)

My conclusions are:
1. EM is good for Economy Class if you want direct flights out from KUL, but only to the rather limited routes it flies to. EM is poor value if you're redeeming Business Class
2. KF & AM is good in that you can fly to many other cities, but the downside (or maybe an upside?) is that there's an additional transit.
3. AM has way higher taxes. (Some of you have mentioned that AM requires less miles than KF, but I don't see too much of a difference, unless perhaps it's because I'm comparing the baseline cheapest redemption amounts?).
4. KF there's potential to redeem their impressive Suites Class & AM you can get Qatar QSuites or JAL Suites.

Updated as requested

if you have no experience in this, recommend you to just stick with CX and redeem through asiamiles website.

if you know how to redeem partner airlines, you can check using:

oneworld : AA website
Star Alliance : ANA website

those are few best search engine.

Within one year after your 1st leg.
That's already a lot!

What kind for travel u need to plan for more than one year ahead?

Yes. Paying via miles ...like 1.2k to extend 3 months? I forgot the extension period

Btw is it the 700 grab point to 160 krisflyer no more?

anyone familiar with accorplus and leclub accor?

i have a leclub gold with accorplus silver, will i be able to book using my accorplus silver and check in with leclub gold to get my free room upgrade?

Spend your KF flying SIA will do.
Unless you have unlimited miles, that's another question.
For SIA, it is more towards which type of seat / plane you are flying.
Same route but it may have a few different flights.
Ie flying Bangkok on 330 vs 787 is totally different experience.
You can always refer to link below:
https://mainlymiles.com/sq-business-seats-by-route/

Just refer to the same list mentioned earlier.
Each flight number has fixed aircraft type for SIA (relatively fixed, but do expect equipment change from time to time especially for short haul).
For Beijing, there are 3 flights daily:
old A380 and 777-300ER (x2); 1 of the 777-300ER will switch into 777-200 from Feb onwards
I guess your wife is flying both of these.

Last year my Suite from Shanghai was cleared 3 or 5 days before departure.
If not mistaken, the seat was 3 of 6 occupied.
I guess they will fill up the seat if there is vacancy and probably with sufficient FA.
As I already purchased the ticket so just ignore.

With new regulation, waitlist will be clear 2 weeks in advance, so you can know the status not till very last minute.
I have a waitlist to Zurich next month, currently it is 5 of 6 occupied, let's see how.

They won’t inform u,  if you comfirm travel on the date, then u must book another ticket first, if the waitlist clear then only u cancel the ticket u booked , coz the chance of getting waitlist clear is pretty low in general

Where you want to go?
For suite, don't just aim for new A380, there are plenty space for old A380 and 777.
Business class, also good amount of space available.
Not forgetting the latest spontaneous escape.
30% off to/from Germany. makes my heart itchy

Haha well,  already prepared to spend since it's a honeymoon trip. too bad SriLankan Air only have 1 seat award for Business, so I have to make 2 separate booking with me taking the last leg in Economy class...

About 2.5 weeks (17 Apr to 3 May). Initially just wanted to get a return ticket to Eastern Europe, but then I discovered Qatar Airways have flights to Maldives, and Maldives got several options (AirAsia, SIA, SriLankan) to come back KL. Initially my gf reluctant to take SriLankan Air as she doesn't want to transit in Colombo because of the recent bombing. But then i managed to persuade her and it helps me to save miles
The online system only can input not more than 4 cities. And also I actually got 3 transits (more than the allowed 2), hence I need to ticket one of the transit as stopover. So yeah, need to call. There is a MY toll-free hotline, 24/7 and is operated by call-center in India I presume

And yes, just search for availability on Asiamiles or Cathay websites and jot down the dates and flight number. It will make the redemption process easier. Took me just about 30mins

Yes senget foot in small hole. But still lie flat, only 2009 rj is angle seat

2017j 2013j and 2006j is senget seat...
The only fully flat and non senget seat is 2018rj