Is there a way to change default settings?
For example I would like to change the default for:
In Board editor:
In Library editor:
- default pad size and shape
In Schematic editor:
can the default symbols on the left of the screen for resistors and caps etc be changed to use my own default devices?
what actually is a ground symbol? how does it work? I think it it is currently the only thing requiring me tio keep the base library installed. My attempts to clone it into my library have not resulted in a symbol/component that “knows” it is ground relative to a ground plane.
No, all these default settings in the library-, board- and schematic editors cannot be changed.
Not yet, but at least this is something I want to make configurable for sure 
No, you don’t need the base library for that (well, I’d still recommend to use the base library since it contains a lot of such useful things - but technically it is not needed). Just open the GND component (not the symbol), there you will see that the “forced net name” is set to {{VALUE}} which is the whole trick since it propagates the component’s value to the connected net.
OK great I see. That forced net name could be useful for other I/O pins, like I could set the name of a a net in IN or OUT or whatever…
It is a useful trick for making disconnected nets a single net for air wire purposes, for example if they are connected in some way off the board.