All of the seminaries will be religious (eg their hanhalas). Blouses=/=more religious. The question is the girls- some more MO seminaries, while with very religious faculty, will have a less religious student body. Some will have a student body which is very religious in a spiritual sense but will not dress, etc in the way you’re used to.
Perhaps talking about the kinds of girls you’d feel comfortable being in school with will help… do you watch movies? Listen to non-Jewish music? Only read frum novels? Are you Zionist? What are your tznius standards? These often have little to do with the actual religiosity of the institution but are important when it comes to feeling comfortable with your fellow students.
Michlalah is a great place, and has had non-traditional students.