After they take the testicles out of the sacks, it's final. The only thing to consider is that males can have live sperm in their system for up to a few months after a neuter, that's why it's advised to wait at least a month or two before introducing him back to an intact female. A neutered male who has live sperm in his system can impregnate an intact doe if put together too soon.
Mounting is a normal part of dominance, so that could be it. Take a few months for the hormones to die down as well, so he's probably still hormonal.
Are the other two fixed?