I am answering second part ' Do other preceptors say that Bhakti can override caste by birth'
Even a person born in a family of dog-eaters immediately becomes eligible to perform Vedic sacrifices if he once utters the holy name
of the Supreme Personality of Godhead or chants about Him, hears about
His pastimes, offers Him obeisances or even remembers Him. They are
worshipable and must have executed all kinds of austerities and fire
sacrifices and achieved all the good manners of the Aryans. They must
have bathed at holy places of pilgrimage, studied the Vedas and
fulfilled everything required. (SB 3.33.6–7)
If a Bramhana has all Brahminical qualifications but is not a devotee
and is averse to the lotus feet of the Lord, he is certainly lower
than a devotee who is a dog-eater but who has dedicated everything —
mind, words, activities, wealth and life to the Supreme Lord. Such a
devotee can purify his whole family, whereas the so-called Brahmana in
a position of false prestige cannot purify even himself. (SB 7.9.10)
If one shows the symptoms of being a Bramhana, Ksatriya, Vaishya or
Sudra as described above, even if he has appeared in a different
caste, he should be accepted according to those symptoms of
classification. (SB 7.11.35)
Yogis are born among all castes; and no caste-odium shall hold in
their cases, for they have seen their souls.(Bharadvaja-Samhita,1.44).
One who is a devotee of Supreme Personality of Godhead can never be
called a Sudra, rather he is glorified as a Bhagavata or one who is
connected with Bhagavan.If one is not a devotee of Lord
Krsna,however,even if born of a Brahmana, Ksatriya or Vaisya family,
he should be considered a Sudra.(Hari Bhakta Vilasa,10.165)
Oh Lord at Sri Rangam! Even brahmins Learned in all the four Vedas
and their six adjuncts, will become outcastes, should they decry Your
devotees in the low caste”.(Thirumaalai,43)
These eight kinds of Bhakti even if they exist in a Mlechha(a
non-Hindu), turn him into a prince of Brahmins, a sage, an ascetic, a
truly wise man.” (Garuda Purāṇa 1.231.9-10)
A genuine Vaishnava is superior to all the Varnas and is the best of
all. (Padma Purana,Uttara Khanda 39)