As far as I know, only statically and globally. You can't switch the MIP level with a function. Not even with custom code, since you can't custom code an asset node, which is essentially just the sampling fuction.
I think that just depends on the options of your shader. It's not realistic to have so many boolean switches ingame as my shader has (like 20 plus), but you can just have a few different versions. For that reason, Pior, I'd never put cubemap reflections in a character shader if you can't turn it off. But hey that's me, I'm…
I`m pretty sure thats what the exact function of a gloss map *in thoery* should do. The blurred look comes from the surface having a roughness to it. the smoother the surface, the crisper the reflection. This level of surface detail, is usually so small however, that its hard to see in real life, let alone at game res. So…
Konstruct, the trick is that the more 'accurate' you go with stuff like gloss maps versus sharp or blurry cubemaps, the more you loose in terms of artistic freedom. Lets say a game allows the blurry/sharp cubemap approach only. If you want to make a sexy glossy look on the lips of a female character, you would get crazy…