Unlike Hauptwerk, Organteq is CPU-limited instead of RAM-limited. The higher GHz and number of cores, the better Organteq performs. Usually Organteq pulls about 125MB of RAM which is basically nothing compared to Hauptwerk, but the CPU use is several magnitudes higher.
Like Pianoteq, which isn't sample-based either, Organteq creates the sound in real time, which greatly increases the processor demands while keeping RAM use to a minimum. Performance improvements have been coming out with each version of Organteq in the past two months, and I would expect that trend to continue throughout 2020.
I'd be curious to hear from Roman or Philippe to know if there are plans in the future for Organteq to "render" the simulated stop sounds and cache them in RAM, which could allow for significant performance increases or larger organ registrations but might not be possible at all in the current (or future) engine.
I get the best performance on my 2.0GHz 8-core CPU by running at 96 Polyphony, 512 Samples (11ms delay), and 44.1kHz sampling rate. That allows for most full organ with couplers applications in multi-voice organ repertory--on my machine. Everyone's setup and results will be different. The lowest acceptable polyphony and sample rate, combined with the highest acceptable delay for your application/situation will result in the highest performance rate with the least "cutting out" of sound.
The other issue with the Novation launchpads not updating is probably because Organteq doesn't send any MIDI-out data as of 1.0.3, which I hope and believe will be implemented soon because there are a variety of functions at organ consoles or custom MIDI set-ups that would be greatly helped by adding MIDI-out or MIDI-through. As a stopgap, you could load Organteq into a DAW to have greater control of MIDI routing in real-time--or something similar to that. I know this particular feature has been asked for in recent weeks, and I hope it's coming soon.
Spotify:
https://open.spotify.com/artist/2xHiPcCsm29R12HX4eXd4JPianoteq Studio & Organteq
Casio GP300 & Custom organ console