I use RIN for turnouts set against traffic (fouling) using the switch machine contact to ground. If you are using the timed approach sequence it is ignored and goes straight back to clear if the block is not occupied.
YIN can be grounded if you want the signal to display approach as the highest speed. RIN and DIN still work as normal. This is useful for some of the restricted and slow approach settings for routes. This can also be used for block detection which does away with the decorative timed approach sequence.
TSCs are useful for interlocking signals where there is more than one route to proceed through.