I think its great that Hinduism recognizes different levels of Rishis.

Order
The superlative title of Brahmarishi is not attested in the Vedas themselves and first appears in the Sanskrit epics.
According to this[citation needed] division, a Brahmarishi is the ultimate expert of religion and spiritual knowledge known as 'Brahmajnana'. Below him are the Maharishis (Great Rishis).
The Saptarishis created out of Brahma's thoughts are perfect brahmarishis. They are often cited to be at par with the Devas in power and piety in the Puranas.
Bhrigu, Angiras, Atri, Vishwamitra, Kashyapa, Vasishta, and Shandilya are the seven brahmarishis.[citation needed] But there is another list of Saptarishi also who are also Gotra-pravartakas, i.e.,founders of Brahamanical clans, and this second list appeared somewhat later, but belongs to ancient period.
All the hymns of third mandala of the Rig Veda is ascribed to Vishwamitra who is mentioned as son of Gathi, including the Gayatri mantra. According to Puranic stories,[citation needed] Vishwamitra was the only brahmarishi who rose to the position out of pure tapas. Originally belonging to the kshatriya caste of kings and warriors, he rose by pure merit to a Brahmarishi. Vishwamitra is also referred to as Kaushika, because he attained Brahmajnana on the banks of the river Koshi.
On the basic level for Rishis. We know they were capable of receiving revelation.