Suggestions Needed - Modular Couch

Seems pretty straightforward to me. The chair doesn't have a lot of sculpted details so creating the mesh wouldn't be that difficult. Before making the model add a mirror modifier but don't apply it. As you model one-half of the sofa, Blender will automatically create the other half. This keeps things symmetrical. Once you're done modeling then click apply. You'll be left with a center seam but you can select that, press X > dissolve edges.

Append an EA sofa into your scene as you model so that you can be sure the height of the seat isn't too low or too high. If it's too high, sims will clip into the seat; too low and sims will float above it.

Use dissolve edges to reduce the poly count for the other LODs. Decimate works but it'll destroy your topology.

If you're planning on using a texture like stripes or something on the chairs, something that needs to look seamless, in the UV editor, press A to select everything, then Alt + O and open your texture. In the 3D window, press N to open the side panel, under shading choose multitexture. Now, you can move your UV islands around and see how the texture appears in real-time.

Ignore the left half of this screenshot. 



Keep in mind that there are slots for where the sims plant their butts. I think you can just delete any slots that are located in the middle (where the table portion of your mesh is). You'll find the slots in the Rig/Slots tab in the main part of Studio. You can add decor slots to the table portion if you want.