Mine's not desexed, and at this stage won't be unless her hips or elbows aren't good enough to breed from her.
I'm planning on showing her and eventually breeding, so at the moment desexing her isn't an option.
I had the same issue with Zali getting rough with the other dogs around 6-7 months where anything that was more submissive than her (usually labs), and she would jump on them roughly in play (although she usually did it on lead, like she feeling threatened being on the lead). As she was also getting a lot physically stronger, I started using a correction collar and the minute she got too rough she was told no, too rough (more for my sake than hers) and taken away from the other dog, especially with other puppies. She could only go back on my terms, if she wasn't too rough. It worked in a very short space of time, as she was obviously just pushing the boundaries. Now, if she's off lead and gets too rough, all I have to do is tell her no, too rough, and she settles down a bit. But the best thing for her has been other dogs telling her off (as long as they back off once she stops), it's really helped her to know that there are boundaries, and she will only get told off by them if she goes too far.
With the mouthing, I guess I know the answers, as squeezing her bottom jaw so her lips press against her teeth works well, it's just training the other family members and people who come up and pat her!! Luckily she is pretty sensitive so will usually stop when told, so I guess it's just persistance and it will eventually stop once she gets the message it's not ok.