A short line will use whatever it can afford to buy, and more important operate.
As to switchers, the entire roster of the Montour RR, a coal hauler near pittsburgh was SW switchers. I think they had about 6-8 of them.
It seems to me the Pittsburgh and Shawmut used a lot of SWs also in all kinds of service.
Shortlines do not/did not have the well defined separation of duties that class Is do. The same engine that makes up the train, often pulled it.
In the last few years, there was a shortline written up in "Trains" magazine that was in the Portland OR area and used an SW as its only loco.
And there was a "Railroads you can Model" article years ago by Kalmbach publications that was about a shortline somewhere down south that had a single EMD F B-unit for its motive power.
I think switchers as both road power and switching would be quite common on shortlines.
Since size seems to bother you, you probably don't want to consider Alco RS1s or RS3 which got handed down a lot to shortlines also.