[ephermeral123]

What are the chances of Amazon opening the box to check its contents, given the seals (although easily replaceable, both by a buyer or an Amazon warehouse worker) look untouched and the weight hasn't changed at all?

There's always a possibility the return will be opened.

Resealing It to perfection, will significantly minimize the risk of being checked.

And what to do should box get discovered?

It can be returned for a legit refund by saying you were In a rush, and mistakenly packed the Incorrect Item In the box.

As to why It was resealed to perfection, you were concerned that an open/damaged box would void the refund, hence returned It In Its original state.

Would buying from Amazon Warehouse make any difference in that scenario (by saying stuff like "you sent me used stuff without checking it beforehand

No.

Goods sold via Amazon Warehouse Deals go through a 20-point Inspection prior to dispatch.

Thanks for the answer!
I'll update with the outcome.

I actually successfully SE'd nanoleaf lights from amazon a few days ago using the DNA method. Very straightforward. They just asked me to fill out an IR. Might be a better option than your sealed box method. Best of luck.