I don't think you can think subconsciously or unconsciously,if the definition of thinking involves higher cognitive functioning where we are aware of what we are thinking.
Sub- means below the level of, and un- mean not. Subconscious actions or functions are those that you are not aware of, or not fully aware of, such as your emotional reaction to someone's body language that leaves you with an uneasy feeling about them, or your observing of things that you see, hear, smell, touch or taste that are incidental to the main thing you are consciously focussing on and your brain stores away somewhere but without your higher recognition of it.
Interesting tests are done with people with split hemispheres or ordinary people looking at two different scenes with each eye that show that the brain can register and respond to things apart from our knowing about it. That is subconscious. But 'unconscious' or 'not conscious' can sometimes be used in this way too. As in "he was not conscious of the effects of his behaviour..." or "she was unconsciously conveying a sense of superiority over her workmates..."
