"Apple Launches Extended Holiday Return Policy, Return Deadline Set for January 8, 2020"

Not sure if you guys have the offer above in Malaysia but here in the US, I can buy a unit to try out and return it a month later if I am not happy with the product. Decided to settle on the 8-core base unit without upgrades. And test it out "kaw-kaw" for a month.
Cheers!

In Malaysia don't have.
No returns.
Exchange if product DOA or defective within 14 days.

I returned few iphones, apple watch and hermes leather watch strap to Apple. 

it is business strategy.
some will buy to try, and end up continue to use it.

Yes, no issue as long as it's a sealed set. Unwrap on the spot, open the device make sure the serial number is valid with Apple.

The only thing is you need to replace the adapter as those are US units.
Warranty wise no issue can walk in an apple store.

But as you said, if you want peace of mind then buy from Apple store is the best.