Sibling play or something else

Our neighbor brought home a 7 week puppy almost 2 weeks ago. She's a sweet girl, fluffy as hell. German Shepherd/Akita mix. T

The following Friday we brought home her sister. Same litter. So literal sisters.

First few days his pup annoyed ours, but they played. She was very dominant and would stand on ours back. Ours has been home for 5 days now and had started getting more into playing. Fighting back, knocking eachother over, chasing and playing. Now they are getting, mean? Like they are angry. More fighting sounds, and little spats with barking/letting the other know it's done or too rough.

But we can't tell if they are progressively getting worse together over the last few days. Or if ours is now getting more comfortable in the environment and this is how they were together before we brought them home.

How do siblings/litter mates usually play? What's normal, what's not? We both have another dog and cats in the home. For us, so far with her supervised interactions has been great with the other animals. Our dog is larger so it's very closely watched because she could pouce and hurt her accidentally but is pretty good. One cat likes her and plays, one is hesitant but warming up. All are friends. Which leads me to believe more that it's normal for her and her sibling to play fight the way they are But I have no idea!