Priestley believed Jesus 100% man, not at all divine in his nature. But he also apparently believed in the virgin birth and the resurrection, two things Jefferson rejected. Priestley's Jesus was a "Savior." A second Adam to correct the errors of the first.
From his "Three Tracts":
If you ask who, then, is Jesus Christ, if he be not God; I answer, in the words of Peter, addressed to the Jews, after his resurrection and ascension, that Jesus of Nazareth was a man approved of God by miracles and wonders and signs, which God did by him. Acts ii. 22. If you ask what is meant by man, in this place; I answer, that man, if the word be used with any kind of propriety, must mean the same kind of being with yourselves. I say, moreover, with the author of the epistle to the Hebrews, that it became him by whom are all things, and for whom are all things, to make this great captain of our salvation in all respects, like unto us his brethren, that he might be made perfect through sufferings, Heb. ii. 10. 1J. and that he might have a feeling of all our infirmities, iv. 13. For this, reason it was that our Saviour and deliverer was not made of the nature of an angel, or like any super-angelic being, but was of the seed as Abraham., ii. 16. that is (exclusive of the divinity of the Father, which resided in him, and acted by him) a mere man, as other Jews, and as we ourselves also are.Priestley doesn't see the virgin birth as a unique sign that points towards a divine nature. He analogizes it to the first Adam's creation. Adam didn't have a virgin birth, because he was not birthed of a woman. Rather both Adam and Jesus were "not born in the usual course of generation" and both were equally 100% human, not divine. Jesus perfected the divine mission of man from which Adam strayed.
Christ being made by the immediate hand of God, and not born in the usual course of generation, is no reason for his not being considered as a man. For then Adam must not have been a man. But in the ideas of Paul, both the first and second Adam (as Christ, on this account, is sometimes called) were equally men: By man came death, by man came also the resurrection of the dead, 1 Cor. xv. 21. And, certainly, in the resurrection of a man, that is, of a person in all respects like ourselves, we have a more lively hope of our own resurrection; that of Christ being both a proof and a pattern of ours. We can, therefore, more firmly believe, that because he livest we who are the same that he was, and who shall undergo the same change by death that he did, shall live also. John xiv. 19.