All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
What you mentioned about some Salaf (righteous predecessors) regarding the permissibility of trimming the beard could be in relation to what exceeds the fist's length. The Ihyaa’ ‘Uloom Ad-Deen authored by Imaam Abu Haamid Al-Ghazaali reads: "The scholars differed in opinion regarding a long beard; it was said: if a man grips his beard and then trims whatever exceeds his fist, this will be acceptable. Ibn ‘Umar and a group of scholars among the Taabi‘is did so (trimmed what exceeded their fist's length), and Ash-Sha‘bi and Ibn Seereen were of the view that it is desirable to do so." [End of quote]
Also, confirming this is the statement of Al-Hasan Al-Basri according to what Ibn Abi Shaybah quoted from him: "The scholars gave concession to trimming of the beard what exceeds the fist's length."
However, this concession is not in relation to trimming most of it, let alone shaving it, as many people do. Ibn ‘Aabideen from the Hanafi School said in Radd Al-Muhtaar: "Trimming the beard could be interpreted as meaning not trimming most of it or all of it as the Zoroastrians do, as they shave their beards." What supports this is that Abu Hurayrah narrated that the Prophet, sallallaahu ‘alayhi wa sallam, said: 'Trim your mustache and let your beards grow. Be different from the Zoroastrians.' [Muslim] So, this sentence indicates the reason why we should keep our beards." [End of quote]
The cheeks are part of the beard; this is what the linguists stated according to the Al-Qamoos Al-Muheet, Taaj Al-'Aroos and other dictionaries. This is what Ibn Hajar mentioned in his Fat-h Al-Baari and Shams Al-Haqq in his ‘Awn Al-Ma‘bood. This is also the legal opinion of the Permanent Committee of Iftaa’, and that of Shaykhs Ibn Baaz and Ibn ‘Uthaymeen .
Nonetheless, some scholars stated that it is permissible to shave the hair of the cheeks; the Book Al-Fajr As-Saati‘ ‘ala As-Saheeh Al-Jaami‘ reads: "The hair that grows on the cheek, the Shaykh Al-Faqeeh As-Saalih Abu Al-Hasan Al-Muntasir did not remove it, while others of the same level as him would remove it." But the preferred opinion is what we have stated above.
Allaah Knows best.