Ramanuja is said to have advocated equality of all Hindus,
This needs to be qualified for it is easily misinterpreted/misrepresented (including by some popular maThas on their websites).
Equal in what way?
The position of Ramanuja (and his followers) is that all living beings (jIvas) are equal from the point of view that they are all eligible for mokSha and they need to resort to the Lord for it.
See Ramanuja Gita Bhashya on 9.29. Van Buitenen renders -
Being a refuge for all, God is the same toward all atmans of devas, men, animals and immovables, which, according to their class, configuration, nature and knowledge, exist in an infinite plurality of forms, from the highest to the lowest.
No one who has resorted to God will be abandoned by God because his humble class, configuration, nature and knowledge is odious to Him;
and no one who has resorted to God together with a humbler votary is more beloved of God because of his more exalted class etc.
All beings who worship God by bhakti whether they be of an exalted or a humble class will at their desire foregather in God as if they share his virtues, and God himself will dwell in them as if they are more exalted than He.
Have prominent Srivaishnavite Acharyas like Vedanta Desika,
Pillai Lokacharya et al expressed opinions on caste
different from Ramanuja's ?
Again you have to clarify what you mean by 'opinions on caste'. As far as eligibility for mokSha is concerned, there is no deviation from Ramanuja's view.
If you're referring to varNAshrama-dharma, then both Vedanta Desika (of the Kanchi school later termed Vadakalai) and Periyavachan Pillai (of the Srirangam school later termed Tenkalai) have explicitly said that just because someone may be a Srivaishnava doesn't mean that violations of other rules of varNAshrama-dharma like intermarriage among Srivaishnavas of different varNas are permitted.