Environment Maps in Cryengine

It depends, is this for folio? Or production?

For production we would minimize drawcalls as much as possible, so we would make this bench only one submat (excluding the proxy submat), and to get the proper reflections on the metal, we would use a gloss map.

For portfolio, use two submats, one for the wood, the other for the metal, you have alot more control this way, you can tweak the mat of the metal to perfection, and for the wood you can even trow a detail map in, to make sure it looks crisp at close distance.

As for cubemaps, if you have a environment probe in the level, then high glossy materials will reflect this environment automatically, asuming you give the probe a proper radious and your prop is within that radious.

Or you can force a cubemap for a specific submat, just put any environment cubemap texture in the environment cubemap slot (there's a few stock ones), and tick 'environment cubemap' in the shader params.

If you want to generate a cubemap for your specific scene, then you would need a environment probe to render one out, obviously.

You should be able to render out a cubemap up to at least 512*512, if it's not working try the 32bit version of the editor, but you wont find much of a difference unless you're making a mirror.