Retrieving motor settings

Yes, you have that right. Any group sent with a null value ("") will return the members of that group. Here are some other examples:

{"2":""} returns motor 2 settings
{"x":""} returns X axis settings
{"sys":""} returns system settings
{"g54":""} returns offsets for G54 coordinate system
{"hom":""} returns system homing state

See here for the JSON overview:
https://github.com/synthetos/TinyG/wiki/JSON-Operation

Here is a list of available groups that are now on the wiki here:
https://github.com/synthetos/TinyG/wiki/JSON-Details

{"1":""} return motor 1 settings
{"2":""}
{"3":""}
{"4":""}
{"x":""} return X axis settings
{"y":""}
{"z":""}
{"a":""}
{"b":""}
{"c":""}
{"sys":""} return system settings
{"pos":""} return work coordinate positions fox XYZABC axes. In mm or inches depending on G20/G21
{"mpo":""} return absolute machine positions fox XYZABC axes. Always in mm, regardless of G20/G21
{"ofs":""} return current offsets fox XYZABC axes. Sums coordinate system and G92 offsets. in mm.
{"hom":""} return homing state fox XYZABC axes, and 'e' for the entire machine. 1=homed, 0=not.
{"p1":""} return PWM channel 1 settings (currently there is only 1 PWM channel)
{"g54":""} return offsets for work coordinate system #1 (G54)
{"g55":""} #2
{"g56":""} #3
{"g57":""} #4
{"g58":""} #5
{"g59":""} #6
{"g92":""} return G92 offsets currently in effect
{"g28":""} return coordinate saved by G28 command
{"g30":""} return coordinate saved by G30 command