How old are the rescues, and how old are the new girls?
What breeds are they? Both new kids and rescues.
Yes, IMO, you will want to keep the groups in a “see no touch” scenario.
....the duration of the separation will have a lot to do w the answers to questions 1 and 2
Assuming everyone is close in age, size, and ....on the less hostile side of the breed range, it could go pretty quickly.
If they react poorly across the fence, it will take more time.
But I usually set up a pen w a temporary hutch next to my main pen.
Let the groups take turns free ranging w supervision.
Once I see the ladies starting to sleep across the fence from the others, I usually start w the all girl group, let them out to free range. And then open the gate for the older/ mixed group, and let them explore together.
If they are brats, I separate for the night and try again the next day.
If they are getting along, I’ll chase them to bed for the night and keep an eye/ ear peeled.
Good luck!