Make the scout design thats best for your particular purpose. If its just for peeking into the next system, 4 engines and no supply might be OK, but for long range scouting you need both. Or you can build whatever you can in one turn and retrofit it to a better design later. Or you can just use colonizers for scouting, no need to give those fuel for the return trip
Never ever divide research evenly. You will loose whatever extra points there is when a project is done. When doing sequential research the extra points carries over to the next project.