Did the Gurus say they were special messengers from God who could do amazing things, or did they say they were regular people teaching a new way to live based on what they knew?

Respected Muskan Kaur ji,
Waheguru ji ka Khalsa, Waheguru ji ki Fateh!

In response to your question, the undersigned wants to say that the First Guru Person, Guru Nanak Sahib, had made it very clear, in his discussion with Yogis, that his Guru was Shabad when he said ‘Shabad Guru Surat Dhun Chela (ਸਬਦ ਗੁਰੂ ਸੁਰਤਿ ਧੁਨਿ ਚੇਲਾ)’.

Therefore, from the very beginning, it was made clear that the Shabad, and not the bodies of the Guru Persons, were Guru. Each of the Guru Persons came with a mission and passed on the baton to next Guru Person, till the Tenth Guru Person, Guru Gobind Singh Sahib, on completion of his mission, closed the lineage of living Guru Persons and ordained Guru Granth Sahib, as ever living Guru of humanity.

The Guru Persons , lived simple lives as righteous/virtuous persons (ਸਚਿਆਰ ਮਨੁੱਖ), as per Divine Law (minus any miracles) and taught the Sikhs also the same.

The humanity was put directly in touch with Akalpurakh (advised to remain one with Akalpurakh, all the time), who is Hukam Roop (ਹੁਕਮ ਰੂਪ), and advised to take the help of Shabad Guru, who is Updesh Roop (ਉਪਦੇਸ਼ ਰੂਪ). The Guru Persons never claimed that Shabad was theirs but made it clear that it was from Akalpurakh, as you may please observe from the stanza of the Shabad below:-

ਅਨਦਿਨੁ ਨਾਮੁ ਜਪਹੁ ਗੁਰਸਿਖਹੁ ਹਰਿ ਕਰਤਾ ਸਤਿਗੁਰੁ ਘਰੀ ਵਸਾਏ ॥ ਸਤਿਗੁਰ ਕੀ ਬਾਣੀ ਸਤਿ ਸਤਿ ਕਰਿ ਜਾਣਹੁ ਗੁਰਸਿਖਹੁ ਹਰਿ ਕਰਤਾ ਆਪਿ ਮੁਹਹੁ ਕਢਾਏ ॥ {ਪੰਨਾ 308}

ਅਰਥ: ਹੇ ਗੁਰ-ਸਿਖੋ! ਹਰ ਰੋਜ਼ (ਭਾਵ, ਹਰ ਵੇਲੇ) ਨਾਮ ਜਪੋ (ਤਾ ਕਿ) ਸਿਰਜਨਹਾਰ ਹਰੀ (ਇਹੋ ਜਿਹਾ) ਸਤਿਗੁਰੂ (ਤੁਹਾਡੇ) ਹਿਰਦੇ ਵਿਚ ਵਸਾ ਦੇਵੇ। ਹੇ ਗੁਰ-ਸਿਖੋ! ਸਤਿਗੁਰੂ ਦੀ ਬਾਣੀ ਨਿਰੋਲ ਸੱਚ ਸਮਝੋ (ਕਿਉਂਕਿ) ਸਿਰਜਨਹਾਰ ਪ੍ਰਭੂ ਆਪ ਇਹ ਬਾਣੀ ਸਤਿਗੁਰੂ ਦੇ ਮੂੰਹ ਤੋਂ ਅਖਵਾਂਦਾ ਹੈ।

Hope it helps. If you have any further questions, please do ask. If you find any deficiencies, please point out the same, for improvement in future.

Regards,
Your Brother