I do not use "live view" to do black and whites, as I can automatically SEE in black and white before I take a shot: having managed a dark room some years ago and understanding zones helps with this:

I'd shot this location before so remembered how the light is at that time of day along with a loose idea of its composition; I knew the chap on the surfboard would come across in monochrome as almost a "punter" and I was waiting for him to get in the position I was wanting.
I'd already decided in my mind for a final high-key "18th century pencil" look (it being Regency Bath an' all), and could visualise how tonally the final shot would look.
The movement was slow enough to warrant ISO 400, as I definitely wanted f11 here.