[unpakwon]

Could you please help me understand the following in bold?

1. Project managers need to be great communicators. There is no way around that fact. The larger the team, the more important communications become.

2. Another category of passive aggressive behavior is overstepping authority, such as failing to ask for approval in advance. There is a fine line between a go-getter and someone who breaks the rules or rebels against authority figures.

In the above, does "a fine line" mean "a small difference?"
And does "go-getter" just mean "able man?"

Thank you.