Don't know how I missed this question until now.
First: traditional theater organs were pipe organs. The big differences are the number of "string" stops, repeating percussion, and things on the "toy counter" for special effects sounds. The other major difference is the "User Interface" with T.O.s using a horseshoe shaped console with stop tabs, whereas church and concert organs use consoles that has angled stop jams with drawknobs. Voicing of the instruments is completely different.
All that said, you'll find that baroque style organs will have few stops (sometimes just three or four) and a tracker action that will not feel anything like a T.O..
Now the conundrum. Pipe organs are very expensive new, or to relocate. Electronic organs from the 70s are free or cheap, but not convincing. A console that is close to AGO or BDO standard is great for practicing no matter what the shape of the console or the convincingness of the voices.
I've got a Yamaha E5AR sitting in my garage that I use to practice church hymns. (Someday it'll come inside when I can round up enough muscle to haul it up a flight of stairs.) Obviously it isn't a great sounding organ fitting somewhere between a drawbar (Hammond) type organ and a theater organ sans horseshoe console.
The ultimate goal for me will be to gut the console then rebuild it with a pair of 61 note "tracker touch" midi keyboards a reasonable computer and hauptwerk http://www.hauptwerk.com/ At the same time I'll update the amplifier and speaker arrays and add midi to the 25 note flat-and-radiating pedal board.
... but first more of the organ needs to fail.
Go ahead and get any of the consoles you like. Do get one that has two or more 61 note manuals, not one of those with offset 48 note manuals. Best of luck; enjoy the music.