Mixing ground between high and low power circuit
I would say that Figure 1 and 2 are not the same. They differ in the following way:

In Figure 2, the current through the emitter of the transistor has to return to the 60V source. The return path is shared by the 5V return path. That means that there will be a potential difference between the ground of the 5V source, and the ground of the Arduino board.

In Figure 1 the 5V source and the Arduino board is virtually on the same potential, but there could be a potential difference between the Arduino boards's ground and the emitter of the transistor. The current from the emitter to the ground of the 5V source will be very small, thus the potential difference should be small.

The Figure 1 design is better than Figure 2. 

Figures 3 and 4 are the same as Figure 1, just drawn differently.