Annoynimus: The Yekkesh community is part of the Chareidi world; RSRH was a recognized Chareidi Gadol. “Torah Im Derech Eretz” is not at all a change to the traditional Chareidi philosophy; as many MO CR members pointed out, Jews have always joined the workforce and many even had degrees like the Ramba”m and others.
However, the Modern Orthodox movement made serious changes to the traditional Chareidi Hashkafa, by negating/ignoring centuries old principals of Judaism, like this separation concept which we are now discussing.
Old Man/Annoynimus: All Chareidim believe in the same Dveykus concept; the difference between Litvaks and Chasidim is to whether Limud Hatorah is the only channel to reach the actual Dveikus or not. Also, Chasidim see the intellectual pursuit as a contradiction to one’s pure emotional Dveykus; whereas Litvaks see one’s emotions and intellect interconnecting and benefiting one the other.