My Daughter is a Sophomore at Tufts but did not consider WUSTL due to location and a bad experience by a teacher who she really respected.
She loves Tufts, but it is far from diverse ethnically, and seems pretty well stocked with New England students. It is also not what I would call “very” liberal leaning- very little in the way of campus protests that are student driven. And I would call the mix Preppy + Nerdy rather than Artsy.
Politically I would say it probably mid-way between Trinity/Colgate and Brown/Wesleyan. For example, I don’t think there were too many BLM protests last year, or if there were, they were short-lived. The percentage of AA students is low relative higher ranked schools (Ivies mostly). Unfortunately the school you are looking for is probably Columbia.
“a lively residential life and small class sizes where discussion is encouraged. Strong study abroad programs as well.”
This sounds like Tufts, although the class sizes are not what you would get at a 2,000 student LAC.
I think Wesleyan might be more what you are looking for.