I know you won't like this answer, but you probably want the Ultra. The Modular Ultra watch face does the things you want. Heart rate on the screen, lots of c

I know you won't like this answer, but you probably want the Ultra. The Modular Ultra watch face does the things you want. Heart rate on the screen, lots of complications (six small ones, one big one in the middle), seconds displayed in several possible ways. Screen turns red automatically in the dark. Sleep tracking should be pretty much automatic. I don't have any fancy schedules configured, although maybe at one point the phone did ask me what my usual sleep times are. It just automatically collects sleep stats and puts them in the Health app. The round watch face preference is definitely a subjective thing. I can't imagine how it works as a practical matter since so much of what makes a smartwatch useful benefits from the rectangle form factor and space.