So they are probably around two months old. By now you should be sure they are all pullets, not that it matters at that age.
What do your facilities look like. How big (in feet or meters) are your various coops and runs? How are they interconnected? Photos could be really helpful with this.
My main concern is that your facilities may be small, especially since you only have a few birds. When I integrate immature chickens the younger avoid the older. If they enter the personal space of an adult they are likely to get pecked. It doesn't take them long to learn to stay well away. For them to do that they need enough room to get away and then stay away. This is more than the square feet numbers you often see on here, especially for just a few birds. Integration just takes more room than after they are all mature and integrated.
There are techniques to improve the quality of the room you do have. That's why photos and sizes can help, so we can see which might work for you. Clutter (things they can get under, behind, or above) can break the line of sight. Separate feed and watering stations far enough apart so they don't have to compete for food and water can really help. Often that means in the run and in the coop. Many people have success with the safe haven concept. That's where they have holes the chicks can get through but the adults can't. Without knowing what you are working with it is hard to get specific.
A little pecking and chasing isn't too bad. The huge risk is when they can't get away and are trapped. If the hens start pecking at their heads they are trying to kill them. That gets serious quickly.
Each chicken has its own personality. Most hens are normal and not too hard to work with. Occasionally you get an aggressive one that is just a brute toward other chickens. Sometimes it is your sweetest hen that is a brute toward chicks. You can't tell until they are together. Most of the time this is not an issue but it is always a possibility.
We go through this all of the time. Sometimes it is really easy, sometimes not but still doable. Good luck!