Real quick, but important question!

http://www.mangago.me/read-manga/beauty_pop/ (this one fits your description fairly well, except it's not genderbender)
http://www.mangago.me/read-manga/warau_kanoko_sama/ (the same as the one above)
http://www.mangago.me/read-manga/ouji_to_majou_to_himegimi_to/ (fits mostly all of them except that she's not really quiet)
http://www.mangago.me/read-manga/hana_no_kishi/ (this one kinda fits all that you described Can't remember if she was quiet or not, but i think she was.)
hope this kinda helps.

http://www.mangago.me/read-manga/say_i_love_you/

http://www.mangago.me/read-manga/ouran_high_school_host_club/

http://www.mangago.me/read-manga/kimi_ni_todoke/

Here are the mangas that have quiet but very strong mc girls that I know xD

Thank you guys
（＾∇＾）

http://www.mangago.me/read-manga/tokyo_crazy_paradise/
http://www.mangago.me/read-manga/he_s_dedicated_to_roses/
they are not that quiet though...

love in the mask (this author has a lot of gender benders. but this one is the quietest.)

Arigatogozaimashita, guys! (=´∀｀)人(´∀｀=)They were all great mangas! Do you guys know any that are really similar to Saver Manwha? That was the main description. Sayonara!