I just went through an interview at Horizon on Wednesday the 19th, so my input is based on that.

For the technical things, I would say you should know at least a good portion of what 121 says about some of the more prominent subject area. Everything regarding alternates for takeoff or arrival, fuel requirements, O2 requirements, duty time requirements....

There were multiple questions regarding the above areas, but it shouldn't be that bad as long as you've been studying. If you know your instrument stuff, you should be alright.

Good luck!