[Lemoy]

but if I use sealing stripes it wouldn‘t be realistic to tell that I have put the wrong Macbook into the parcel.

Simply say that you carefully opened the box and resealed It without damaging It - just to make sure that there's no Issues with the refund, If a damaged box Is returned. 

I can come up with an array of excuses/reasons for the return.

But it also isn‘t realistic that they open a box which seems to be untouched which is a plus point for me.

Precisely.

If there's no Inconsistencies with the box, It does not give them reason to check/open the return.

Would you recommend Amazon or Apple for this method?

Amazon has a higher success rate.

Would Apple probably have the chance to trace back to me? (if I get a refund) Over the serial number and used apple account maybe?

Once It's sold, who's to say the buyer (who purchased your return) Isn't an SE'er attempting a refund?

You‘re just perfect! Thank you very much.
Could we say that this is one of the highest success rate methods and you may get anything if you may do it so it looks untouched?