if use Arnold operators you can change shading and geometry without any delay in IPR rendering. Operators toegther which Houdini node graph and you have simpler version of Solaris, Katana or Gaffer. the Arnold operators are around for years when even Katana and Gaffer was quite new and long before the idea of Solaris.
Operators allow advanced users to override any part of an Arnold scene and modify the Arnold universe at render time. Probably one of the most common use cases is to override parameters (e.g. shaders) inside a procedural (USD, ASS or Alembic).Here is quite test with 600GB caches file during Arnold GPU interactive rendering.
As you can see its quite fast to update the interactive rendering. you can the Kick command which used to query possible target node parameter names of a set_parameter node. For example: kick -info or kick -info polymesh. a more detailed tutorial i will do in future posts.
i've used a set parameter to change the radius of the foam particles. radius *= 1.3 or change the particle to 'disc', 'sphere' or 'quad', o change the shader like shader == 'purple_shader' .
here more detail talk about usage of arnold operators from autodesk and The Mill.