in practice, you can usually make stairs any size you like that looks "right" and shove a player clip volume over the top of them to create a smooth ramp. what looks right can depend entirely on the stair's context and surroundings - tall, narrow stairs tend to create a cramped, old-fashioned feel while broad, short steps look more modern and open.
I personally find myself using 1 up for every 2 forward more often than anything else.