there's a great but not well known editor for windows called EmEditor that has a strong emphasis on performance and large file support. afaik the author has a background in low level performance optimization from Intel. if you work with large csv and/or json files you want this editor - it's amazing!
Suzukawa Editor (Japanese shareware) is interesting project. It claims it's the best editor for huge gigantic file. It compares with EmEditor in official page and it performs unmatched performance.
I haven't used this because I have no chance to edit such gigantic files.
