The squealing is submission. Unfortunately, we cannot judge whether the dominance you are reporting is excessive or not. Please keep in mind that new leaders can be very insecure in themselves and overcompensate; this usually settles after a little while. Keep in mind that pet shop babies are in their 'school weeks' between weaning and teenage whether they would normally attach themselves to an older piggy and learn to master the the finer points of cavy etiquette and how to master their environment by shadowing a willing teacher pig. It can be a daunting task having to step up as a leader by default when you are not feeling qualified.
Please take the time to read about typical sow dominance behaviours in this helpful guide here:
Sows: Behaviour and female health problems (including ovarian cysts)
Journey through a Lifetime: The Ages of Guinea Pigs
Unfortunately, without direct access to your sows, we cannot comment about the general situation bacause we can basically only make guesses based on your assessment but not judge whether this is correct or not - which is what you are asking us to do for you.
It would help us if you could please copy a video that you have uploaded on a public setting elsewhere into this thread since we don't have a supported video uploading facility (the forum is entirely run by voluntary member donations).