Apparently I'm an oddball because I rarely "envision" a song.
Just as I strum my acoustic to find interesting chord progressions (which can end up in a ballad, a punk song, a pop song, a rock song or anything in between), I "strum" the keyboard in BIAB and play with different styles, realtracks, and arrangements until the song itself tells me what it wants to be.
The working title for my tribute song "Surviving your idols" was "Heavyrock in 3/4" and it's probably the softest ballad I've written in a long time