I just did a pretty huge architectural project on Octane, from my experience here is a couple of tips:
- Don't be afraid of polygons, it can handle lots with little performance impact, but be aware of textures, those can eat your vram away. I had 1,5M poly using under 300Mb and octane runing smooth as hell.
- Pack your textures, Octane has a limit on how many different texture files it can handdle, so pack some of your textures so you can have more variation with fewer texture maps, also reuse them as much as you can 'cause once in the scene doesn't matter in how many materials they are in.
- When in doubt choose a mesh over opacity, opacity maps kill the performance, so it's better IMO to make "holes" in your mesh in almost any situation.
- For the alpha make two copies of your mesh, one the regular mesh, and the other one the "all black" one with plain diffuse materials for the matte objects, black diffuse with a little opacity for the glass, and black with opacity map for the clipped images, you can load both in octane set the camera and switch to the "alpha mesh" once the other shot is done, or easily batch render both from command line.
-If it's for you, there is no problem, but if you have an external client be aware of showing test renders to early, octane is too damm fast and they'll think they can make lots of changes with the same deadline, althou that it's true, it's a total pain.
Have fun, if I can think of anything else I'll add it later