Tim,
The RCS Standard Gauge switches are drop-in replacements for the MTH switches. However, their footprints are not the same primarily because MTH switches have wide/long/large switch motors permanently attached on one side of the switch. RCS switches do not. Instead, they have narrow LGB switch motors, which can be attached to either side of a RCS switch depending on what the track plan requires. This feature permits tracks to be spaced closer together than is possible using MTH switches. Below is a photo of an RCS switch sitting over an MTH switch. In the photo you can see both the large MTH motor sticking out on the lower MTH switch and the much smaller LGB motor attached to the upper RCS switch.
One important difference is that unlike MTH switches the LGB switch motors on RCS switches require DC power. That said, there are switch controllers specifically designed to operate LGB switch motors such as the below Piko control box, which converts any input current, DC or AC, into the precise DC output current required to operate up to four LGB switch motors.
Bob Nelson