It depends to some part on the boars. Boars that have always lived with sows in the same roon/shed are often not too bothered, whereas boars that have been together on their own will react much more strongly and can fight and fall out, especially boars during the stroppy months when their relationship is under strain anyway.
Ideally, you want to keep the different sexes at opposite ends of the room, well out of sight and reach of the sow pheromones when they come into season. If that is not a possibility, you'd better keep the boars above any sows to minimise them being affected by pheromones.
What is not ideal is keeping sows and boars directly next to each other and in line of sight. That will cause problems with even the most laid back boars!
If they use the same run, always let your boars out first, for the same reasons.