Should have judges a past choice, could have names an option that existed, and would have imagines a result you believe was certain. All three can fit a soft hindsight comment; in casual speech, should have called and could have called differ only in tone, regret versus neutral possibility.
The pair needing real care is could have won against would have won: possibility versus a settled outcome.
Choosing between them in real sentences
You missed the deadline. I should have told you earlier blames yourself for not acting. I could have told you earlier only notes it was possible. Pick should when judgment is the point, could when you just mean the option existed.
Your friend missed the bus. You should have left at eight criticizes the choice. You could have caught the earlier bus points to a real chance without blame. Same fact, different attitude.
The match was close. I could have won says winning was possible but uncertain. I would have won imagines a result that did not happen, usually because something intervened. Your confidence in the outcome decides the wording.
Sometimes the choice changes the tone, not the truth. We should have stayed and we could have stayed both work in conversation, since both show hindsight. Should adds regret; could stays neutral. For the softer version, could is the safer pick.
One exception should change your choice outright: should have can state a plain past expectation that may well have come true. The package should have arrived by now means you believe it arrived, though you are not completely certain. Here could have would sound like a mere possibility, and would have would add a hypothetical twist the sentence does not need.
Outside that expectation use, the clearest boundary is certainty. I would have called you is a settled judgment: the call would have happened if circumstances allowed. I should have called you still leaves room for doubt about whether calling was right. If you are unsure what the right choice was, should is the honest one.
Where both fit, the choice is about confidence rather than grammar. With those prices, I would have bought two and I could have bought two both work when the possibility and the imagined outcome almost coincide.