You can do both of those things in both of those phases. The phases are less about "phase X does this, phase Y does this" as they are about who and how many are in the phase. This gives you the power to look at different things.
In phase 1, you have a few healthy people. This lets you see what side effects there are in normal people, along with how much drug gets you to those side effect (i.e. side effects, dosage range).
In phase 2, you have a medium group of sick people. This lets you find out if the drug works at alleviating symptoms. It can also let you see if there are certain side effects specific to sick people, or if the dosing is different in sick people. However, efficacy in sick people is the main draw of phase 2.
In phase 3, you have a large group of sick people. This lets you really put the efficacy to the test, especially since you can compare it to gold standard treatment to see if it's better. You can also see less common side effects, since your group is bigger.
Finally, phase 4 lets you see the effect of the drug on the whole population of sick people, and (hopefully) lets you see the rarest side effects.
All of these phases let you monitor safety and side effects, and phase 2-3 specifically let you see how good a drug is (efficacy).
