Column profile is set by two parameters, one is bubble point and second one is available utility conditions (such as, available steam pressure & hence steam temperature in case steam being the heating fluid, that governs column bottom temperature). In case, available utility cannot meet required bubble point condition, you may have to operate column under vacuum, so that bubble point will be less by 5ºC than available utility temperature.
Once your column bottom temperature & column bottom pressure gets fixed, subsequently column top temperature is nothing but dew point at given pressure.
If you are designing completely new plant with no utility available, you need to optimize the conditions. It is always costly affair to operate column under vacuum. As far as possible, you shall run column near atmospheric pressure. At the same time, raising steam temperature & hence pressure calls for all allied hardware of higher rating. Considering both the aspect in mind, you need to fix column parameters.
Hope, this answers your query.