Gargraves is not compatible with scale wheels.
The cross section of the rail is nearly identical among SHS/MTH, Fox Valley Models and Lionel FasTrack. They are compatible is the sense that they butt together and you can use rail joiners from any of these brands interchangeably. But if you are using sectional track rather than flex, then you need to modify as Ray mentioned above because SHS/MTH and FasTrack do not click together. Fox Valley Models does not make sectional track.
My recommendation is to use flex track from SHS, MTH and/or Fox Valley models. They are compatible with each other, and you can use rail-joiners from any of them to connect to whichever brand of turnouts you select.
