When I first got started, I got hung up about sails design, ballast, etc. On working models, there is no need. There is a fundamental difference between working boats, and racing boats (real or models).
Racing boats are designed for speed. Weight and drag are minimized, while forward thrust is maximized.If we just think about those for the fin keel for a moment.There are hideous calculations for maximizing the righting moment, while minimizing the drag of the fin keel. If you lengthen the fin keel you can reduce the weight of the fin keel required, but you will increase the drag. If you have a fin keel bulb this also helps. There are also the effects of scale and water density, the larger the model (everything else being equal/to scale) the shorter (relatively) the fin keel needs to be to achieve the same righting moment.
Efficiency = speed over the water.
Working boats (with the exception of clippers) were designed to carry the largest load, at least cost, at an acceptable speed for that trade. The surface area of the hull is far larger (comparatively) and so is the buoyancy. I have a working model hull and 13KG of ballast took it down to the waterline. I could easily add/remove 2kg and she would still sail well.
Schooners are usually working, but sometimes pleasure craft.
On sail plans. For racing boats, these are usually fixed by class rules, but change with the weather conditions. The same is true for my model schooner. I don't have different sail sets, I just remove sails. I have also significantly altered the sail pattern on my Mary J Ward model, mostly for aesthetic reasons (skippers fancy). In the pictures you can see different sail set ups. I could even remove the flying jib.
The final factor is wind. There are some boats that are known to be good in light winds, others better in moderate winds. One reason the J Class races (real world) of the early 20th century fell out of favour is that the boats were so finely tuned, that they could only race in light weather. The boats had reached the pinnacle of speed, but so many races were cancelled due to the boats not being suitable for heavy weather that people lost interest in the events.
On working models the aim is to get the boat to function satisfactorily, not to squeeze every last knot out of the design. To some degree, I am more interested in how the boat looks on the water, and with that in mind, the lower in the water, the more impressive the wake of the boat in calmer waters, and the more stable in rougher weather; but she will be slower.