I don't expect to be able to edit or create rhythms in detail. In multitimbral sound generators, the level of the single parts is an essential parameter. This has nothing to do with optimization, but rather with adaptation to one's own listening habits and/or the current musical context. From this point of view, a rhythm cannot be optimized at all. I almost always mute individual parts of styles/rhythms or reduce the volume of certain parts. This often reduces the cheesy character of a typical accompaniment.
No, not DSP effect parameters. I actually meant the Casio's few sound parameters like envelopes, modulation, effect send etc. See pages EN-94 / EN-95.
Thank you for the very helpful link. This does not solve my basic problem with the rhythm part levels, but expands my choice of available styles.
The analog chorus effect of an early 80's synthesizer is hard to compare to the capabilities of a current digital keyboard 😉. When I work with delay effects, for example, I want to have access to at least the delay time and feedback. That's really not too much to ask in the context of any delay fx.
Anyway, thanks for your time to answer my questions so detailed.