Q: Various languages assume particular machine implementions of the commands that run with particular hosted side affects. If “the same” visual commands run on another machine, the side effects may be noticeably different in ways that matter and/or create error. How should this be addressed?

A: For each platform implementation, define a homomorphism from the visual interface into the more complex command set. Simultaneously define a set of side effects that may be observable on that platform, define which are fixed & not controllable, not fixed & not controllable, and which can be controlled in some way by the user, possible through additional special menus. Document that & allow user looking for new platforms to access to the info.

Q:The more expressive forms allow more possibilities while adding complexity. How should the tradeoffs be evaluated?

A: The comment about skins could be interpreted in some precise way. If these N things are the essential tasks, you code make a Hammming code for the expected number of mouse clicks or taps to perform each. Consider also the complexity of reaching the instructions to know what each do. If a domain wants to make it ez and quick to do the common tasks, while allowing a route to more complex ones, then interface platform should make it easy to structure that. The key is to understand the mechanisms of the simplest interfaces to make sure they are covered.