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I think the simple answer to this is either ‘it’s complex’, ‘it depends’ or ‘nobody knows, why don’t you do a PhD on this topic and come back and tell us’.
Even then, I think an accurate answer is really going to boil down to ‘it’s complex & it depends on lots of things, including individual genetics’ - although I expect the complete answers are more or less known for some compounds.
Potassium in it’s raw form is unstable and will even start a chemical reaction with water, so you don’t have a choice with that particular element.
I know that there are multiple forms of Vitamin A and one of them is more absorbable than all the others, while some are completely unusable (if I’m remembering correctly). I’d assume the same applies to most other things.
The body will use potassium as an ionic solution, so you can’t take 3.4 grams of metallic potassium powder, even if you disregard the fact it would burst into flames in your mouth.