Okay to get off earlier Sunrise Izumo?

Hi,
If I reserve a train trip to Izumoshi by Sunrise Izumo can I get off at Matsue if I change my mind? Or would the conductors be looking for me in Izumoshi station?

you can just hop off at earlier stop

You can hop off at any stop. You can also hop onto the said train, at any station.

It is possible to get off at an earlier station, but your limited express ticket will become invalid when you get off. However, your base fare ticket remains valid, and you could use it to take a local trains from Matsue to Izumoshi Station at a later point within the ticket's period of validity. If you have a Japan Rail Pass, then it is no problem either, to get off early.

You can also hop onto the said train, at any station.

Only if you have a compartment reservation for the section traveled. But it is not recommended to get on at a later station than specified. Especially if you get on much later than specified, the conductor may conclude that you are a no-show and free up the compartment for use by somebody else.