Output stage using 2 transistors
No, it isn't a Darlington configuration, because T1's collector is tied directly to ground, rather than to T2's collector.

The advantage is that T2 can fully saturate, reducing its C-E voltage drop and power dissipation.

R2 serves to keep both transistors off when the input connection is open, and you should keep it.

C1 probably doesn't do anything very useful. It limits the rate of change of the voltage on the collector of T2 when it shuts off (depending on the load current), but it also means that extra current must flow through T2 when it turns on. If it is needed at all, it would probably be better to connect C1 directly between the output terminal and ground.