Unless you’re building a large empty warehouse on purpose, it’s better to scale down your builds to a more manageable level. It will save you from the frustration of “wanting to fill space up” and it maximizes playtime otherwise wasted on your Sims walking from point to point. Use placeholder furniture to get an idea of how wide and open the rooms you made really are. Have your sims stand next to the wall or use the mannequin if you have GTW to get a sense of scale when decorating vertically (useful for placing paintings and other wall decor). :)