For the Paramount 341: go to View > Large floating control panels (for this organ) > Recorder/player. You should find that the “Paramount341Demo” MIDI file loads automatically, unless you’ve already used the Recorder for your own playing. Click on the Play button, and you’ll have 18 minutes of music to listen to, with the registration displayed. Make sure you are on the “All Buttons” screen so that you can see all the stops in use. Although I haven’t tried it, it should be possible to save to pistons any registrations you like – either as General pistons for the whole organ, or for an individual manual.
I don’t have the Paramount 450 set up at present, but there’s definitely a MIDI file supplied with it, and it probably loads automatically too. If you aren’t able to find those demo MIDI files you may need another post here to request that information – I haven’t been able to spot their location with a quick search.
Some organists who post Hauptwerk videos on youtube show their registration, though not necessarily throughout a piece e.g.
https://www.youtube.com/watch?v=UVkqszk ... CN&index=7The Contrebombarde site
https://www.contrebombarde.com/concerthall/home/fronthas mainly mp3 files, but some organists also provide youtube videos – where this is the case it’s shown on the site.
Tim Horton has a series of instructional videos on theatre organ playing – start here:
https://www.youtube.com/watch?v=gOJJy5N52lcAs an American you may not be aware of the playing of some of the older British theatre organists - particularly the remarkable Reginald Porter-Brown, who was known as "the organist with three hands", because he was able to use second touch to play melody and accompaniment in his left hand alone:
https://www.youtube.com/watch?v=KwOc07U7vhA