In my limited experience, rafts are really only useful if you don't have sufficient part surface area attached to the bed. With ABS and the way it shrinks, its very likely that a low surface area part could pull away from the bed during a print. In this case a raft could assist by providing more contact area of ABS onto the bed.

If you are, for example, printing a roll pin (no, nobody is printing roll pins but run with it ok?) standing up vertical on the bed, there would be very little surface area of the part to adhere to the bed. It could dislodge during printing. If you put a raft under it, the wide area of the raft would attach to the bed better. Obviously the wise choice would not to be adding a raft but to print the part horizontal in this case. But I suppose there may well be a good reason you don't want it printed that direction, say direction of layer orientation would be one example.

I haven't been doing this very long but I have only printed a raft once.

As for a brim, I usually go with 2 traces over 4 layers when .2mm layers or smaller. 2 layers if I am printing >.2mm layers. Anything less and its a pita to remove the brim from my PEI bed.