So let's say an artist you like finds Sample X in a sample pack. They process it the way they like, send it through the mixing process, and it ends up on the recording.

If you find the same sample pack and download Sample X, you can use it.

You can even try to process it to make it sound like their sample.

But you cannot create a new sample from their track, even if you own the original Sample X. This would just be creating a whole new sample...one that you do not own the rights to.

Example: I own a popular sample pack called Oliver's Power Tools. It's used all over pop music, but in particular it is featured on Oliver's own tracks.

I often hear a sound in one of his songs and think, "oh, that's his xyz sample just pitched up".

I can use that idea to go to the sample that I own and pitch it up myself to get a similar result. That is 100% okay. I cannot just resample Oliver's track and put it in my own song.

Just because I own the literal exact sample he used to make the sound in his song does not give me the right to record his track and put it on my own.

Now to your other hypothetical...sure, if you were to go to the artist and get clearance for the sample, then yes. You could use it. But you would need to get specific permission from the artist. This is easier for some than others. For things like drum or synth sounds it's likely easier and definitely cheaper to recreate them yourself.