As far as mixes being more or less energetic than a GSD, you won't really know! Like sit, stay said generalizations are helpful but not predictive. I have mixes with more energy than some GSDs.
For the females, nothing, including spaying, takes away the "femaleness" that will create the problems in terms of fighting. These things include being fine for days, weeks or years and then all of a sudden an intolerance of monumental proportions erupts, the desire to permanently remove the other female from the home for good, the inability on our parts to redirect or change that behavior using anything but crate/rotate type management of true 100% separation.
I worked in an all boys school, then worked in an almost all girls school. The boys would get into a fight, I could step in, tell them to knock it off and by the time they got to the office to talk about what happened they were goofing around again. If the girls got into a fight, it lasted forever and we would sometimes have to change their schedules so that they didn't have classes (particularly low supervision opportunity classes like PE) together anymore. I never looked into the science of the why, but have found dogs to be similar.
I have multiple females, all spayed - which I do believe helps, living in the house together, and have 2 that require some supervision or need to be kept separate if I am working at home. They have a VERY weird relationship because they seem to enjoy picking at each other and do not seem to want to go above a certain level of snark. But with 5 girls I watch them closely and they aren't allowed to go all "middle school" on me.
However, I never leave more than 2 of any dog out uncrated, unsupervised if I am gone no matter what, and typically crate them all.