The sizers aren’t a true representation as implants look different on everyone, and of course whether you have overs or unders and what profile you get. I’m not sure what profile the sizers are but that makes a difference to your result, as do your natural breast tissue and previous size, as the more breast tissue you have the bigger the implant will look.
375cc is a good size, definitely not too big. I had 375cc but mine were partials and Ultra high, and my previous size was 32AA. I’m now a 30DD or 32D, as I started out with nothing. But if you’re already a C and getting overs, then 375 should take you to something like an E.