Does LC_CTYPE affect performance, index use?

I've read that setting LC_COLLATE to something other than "C" / "POSIX" negatively affects performance, and disables use of indexes for LIKE, etc...

Does the same apply to LC_CTYPE?

I am considering setting LC_COLLATE = "C", and LC_CTYPE = "en_US.UTF-8", and using LOWER() to case-fold strings for sorting, and equality. The motivation for setting LC_CTYPE = "en_US.UTF-8", instead of "C", is to gain at least some degree of case-folding for international characters.

Does this sound like a reasonable plan?

Thanks,