Editing is a very important step, but you cannot overdo it.
Before mixing you should prepare the session. You need to cut all noise. Using the instrument “scissors” Remove all possibles clicks. If you cannot make that using volume automatization, you need to automate the inclusion De Clicker plugin so that it only turns on at the time of the click. This stage is like cleaning the workplace. Everything should be very streamlined and decomposed.
Next, you need to align the back vocals with the lead vocals in time. Ideally, you need to cut all breaths from the back vocals and move them to a separate track. You will need to do this for the lead too.
Breaths should be on a separate track. That will help the mixing engineer to control the volume of breath after compression.
Also, you should make the tuning vocals here, use the Melodyne or Vari Audio (Cubase) для Manual Vocal Correction and AutoTune for automatic pitch correction.
It is worth noting that with manual vocal correction you have more tools and opportunities to influence vocals. As a result you will get more professional editing, if you can handle these tools.
In general, the session should be completely ready for mixing. Mixing engineers shouldn’t work on restoration and fixing recording issues. They should work with balance, making the painting.
If in the editing process you cannot fix something (noise, click, tune), you need to come back to the previous step and change the sound.
As I’ve already said, nobody can fix this mistake, and at best it will be disguised. But this is not professional, is it?
Also, I can make an example with making movies or video clips.
If on site, somebody sees that the camera is shooting somehow wrong or someone went into the frame, or some noise appeared on the image, will people turn a blind eye and simply pass it on to editing, or will they reshoot?