If the lighting in your game is mostly static or sharply toggles between a few modes, then don't use normal maps and just hand-draw the highlights. Static highlights that don't quite match the lighting usually look fine and players don't notice them. However, if you have dynamic lighting, then dynamic highlights (and/or shadows) to match it can add a great bit of extra visual polish.
Normal maps + automatic lighting on pixel art rarely look as good as manually-drawn lighting, and this is compounded by automatically-generated normal maps usually having some kinks. You will probably want to manually tweak your normal maps to make them interact with your lighting just so, e.g. to emphasise important details or flatten unimportant textures.
Your unlit sprites should probably have ambient occlusion (non-directional shadows in crevasses where light doesn't tend to reach), but no directional lighting or highlights.