Come over here.
Get over here.
Do these mean the exact same with the only difference being that the second one sounds a little more like an order?
"Get over here!" is extremely disrespectful in any context I can think of.
Angry mother to unruly child: Get over here! You have been misbehaving all day!
Bank robber to customers: Get over here and lie on the floor before I shoot you!
"Come over here!" is peremptory or enthusiastic depending on the context and tone of voice.
Teacher to pupils: All of you come over here. I want you to see this insect from close up.
Friend to friend: Quick! Come over here! There's an amazing acrobat performing in the street!
I think that they essentially mean the same thing, and as you said, that get over here is more like an order, but I also think that it is a matter of distance. If you were talking to a colleague across the room, you would probably say; 'come over here,' because all they have to do is travel across the relatively short distance between where you are and where he is. But if you were say, in the UK, and you were asking someone to join you who is in, for instance, Japan, then you might use get over here because they have a longer distance to travel than just walking across a room. Although you could also use come over here in that case and it would be perfectly acceptable.