So I'm not asking if anyone really did magic or communed with the devil in unholy sabbaths or rode broomsticks through the air or had cauldrons etc. But is there any account of a person or persons who existed during the early modern period when witch hunts were at their peak that actually identified as such without being forced to confess or otherwise? If such a person existed, what did a "witch" actually do?
Setting aside the concept of healers and ‘white witches’, which is a whole different kettle of fish, a simple answer to the first part of your question would be, yes there were people who confessed to being in league with the Devil without being coerced. They were a minority, but there are confessions and testimony that appear to have come from people who had not been subject to any ordeal, or torture, or coercion.
Two that immediately come to mind are Alexander Sussums and Margaret Moore, two “witches” who were tried during the English witch panic of 1645-47. Alexander Sussums approached John Stearne, a “witchfinder”, and requested to be searched for the witch’s teat. Sussums directed him to his teats, and confessed that he had been suckled by imps for sixteen years. This was enough for Stearne, and the witch-finder ordered Sussums arrested and prepared for trial. The teat was a supposedly-unnatural growth that was used to feed a witch’s imps or familiars; the problem was, almost anything could be judged to be a teat, from a blemish, to a wart, to haemorrhoids. Sussums went to trial, and even confessed to being a witch, but was acquitted by the jury. Margaret Moore, a woman with a poor reputation in her home village of Sutton, seems to have willingly confessed to her local magistrates that she was a witch. She doesn’t seem to have been subjected to the Watching, where suspects were deprived of sleep until they broke, or any sort of coercion. She later repeated this confession twice, once to John Stearne and then again when on trial for her life. Margaret Moore was not as lucky as Sussums, and she hanged.
The question of why these people would confess to acts that they could not have physically committed, especially when they risked execution for doing so, is incredibly interesting. Aside from more general considerations like mental illness, a theory put forward by Malcolm Gaskill is that in these highly religious societies, guilt manifested in extreme ways. If you had an argument with a neighbour, and in your anger cursed them only to later hear that some misfortune had befallen them, you might wonder whether it had been your doing. If you acquired a reputation for being a witch, due to a series of unfortunate events like this, you might begin to believe that you were, in fact, allied with the Devil. One woman was convinced that she was a witch, purely because her mother was 'known' to have been one. There are also those who, out of desperation and need, convinced themselves that they weren't as powerless as they seemed, or that they couldn't be alone when they had their familiars. The Devil was real in these communities, and no matter how much the authorities tried to stamp it out, popular beliefs held that the Devil could work wonders in the physical world.
Another theory that I think holds water is that social and gender expectations, when failed or disrupted, manifested as guilt. This best applies to the circumstances of Margaret Moore; she had lost three children in infancy to sickness, and when her final child became ill she claimed to have been visited by the demons in the images of her deceased offspring. They promised her the chance to save her remaining child, if she gave them her soul, which she naturally did. It was her job as a mother to nurture and protect her children, and (so the theory goes) her grief over their deaths was amplified by her perceived failure in her role as a mother. It is entirely within reason that, much like people do today, Moore suffered from hallucinations brought on by the loss of her children, and in the context of a religiously-dominated world, ascribed these apparitions to the work of the Devil.
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