The lack of clear goals is one of the reasons 3D furniture modeling
projects take longer. It's critical to have a good sense of measurements, material, and general object layout for lifestyle images and shot composition in general. Using ready-made 3D models or not isn't a big deal either; using such materials lowers order completion time. It will take less time to make small changes to an existing model than it will to create one from scratch.
Choose 3-D models that represent your product from different angles and in various settings — this will give you more options for post-processing and final image selection.