professional singers can use microphone recording technique to achieve sort of 'compression'
ideal is if when they sing loud they get back from mic, and when sing quiet - get close
if they do it correctly - you don't need to compress a lot- maybe nothing
IMO, its a matter of choice. How you want your vocal to sound like? Without any clear idea, this question makes no sense. Mixing is not as simple as 2+2=4. More you experiment, better you will get.
But if you want your vocal to sound like someone you might have heard, mention that first, and then ask the question. Trust me, we started at some point and we all had these kinda questions.